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BIOLOGY 
UBRARY 


PARASITOLOGY 


THE  MACMILLAN  COMPANY 

NEW  YORK    •   BOSTON  •   CHICAGO   •  DALLAS 
ATLANTA   •   SAN  FRANCISCO 

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THE  MACMILLAN  CO.  OF  CANADA,  LTD. 

TORONTO 


A  LABORATORY  GUIDE  TO  THE  STUDY  OF 

PARASITOLOGY 


BY 
W.  B.  HERMS 

UNIVERSITY   OF   CALIFORNIA,    BERKELEY,    CALIFORNIA 


THE  MACMILLAN   COMPANY 
1913 

All  rights  reserved 


350LOGY 
LIBRARY 


Copyright,  1913, 

BY  THE  MACMILLAN  COMPANY 
Set  up  and  electrotyped.    Published  May,  1913 


PBB38  OF  T     UOBET  &   SOW, 
GREENFIELD,  MASS.,  V.  3.  A. 


FOREWORD 

With  the  rapid  growth  of  Parasitology  there  is  also  a  growing 
demand  for  laboratory  instruction  in  this  field.  The  author's 
greatest  desire  during  the  time  that  he  has  been  engaged  in 
teaching  this  subject  has  been  to  place  the  work  upon  a  good 
systematic  footing,  giving  it  proper  rank  with  other  phases  of 
applied  biology.  The  following  exercises  are  based  upon  several 
courses  in  Parasitology  (now  merged  into  two)  that  have  been 
given  by  the  author  at  the  University  of  California  during  the 
past  four  years,  including  two  summer  sessions.  Each  exercise 
has  had  careful  testing  in  the  laboratory  and  is  practical. 

The  aim  of  this  Guide  is  to  give  the  student  a  wide  practical 
view  of  the  field  so  that  he  might  have  a  fair  grasp  of  the  general 
subject  in  its  application  to  the  health  and  well-being  of  man  and 
beast.  The  exercises  are  in  sufficient  detail  so  that  the  student 
is  enabled  to  continue  work  on  some  specific  group  or  species  if 
he  so  chooses. 

The  exercises  are  arranged  to  provide  sufficient  matter  for  a 
laboratory  session  requiring  from  two  and  a  half  to  three  hours 
for  each.  A  number  of  the  exercises  are  divided  into  two  or 
three  parts,  and  this  may  be  useful  in  cases  where  less  time  is 
available.  The  two  standard  courses  given  at  the  University  of 
California  upon  which  these  exercises  are  based  are  Human 
Parasitology  (first  half  year)  and  Veterinary  Parasitology 
(second  half  year),  each  with  three  lectures  per  week  and  two 
laboratory  sessions  of  from  2>£  to  3  hours. 

The  author  wishes  to  gratefully  acknowledge  the  very  able 
assistance  rendered  by  Mr.  A.  B.  Shaw,  Jr.,  in  the  preparation 
of  this  laboratory  guide. 

W.  B.  H. 

BERKELEY,  CALIFORNIA, 
August  5, 1912. 

T 


7  ft 


CONTENTS 


PAGE 

Introduction.  .  xi 


PART  I 

MEDICAL  ENTOMOLOGY 

Insects  and  Disease.    (Discussion.) I 

A  Study  of  Insect  Mouthparts.    (Exercise  i.) 8 

A.  Orthopteron  type. 

B.  Hymenopteron  type. 

Insect  Mouthparts  (cont.).    (Exercise  2.) 10 

C.  Hemipteron  type. 

D.  Lepidopteron  type. 

E.  Dipteron  type. 

a.  First  subtype,  the  Mosquito. 

Insect  Mouthparts  (cont.).    (Exercise  3.) n 

F.  Dipteron  type  (cont.). 

b.  Second  subtype,  the  Horsefly. 

c.  Third  subtype,  the  Stablefly. 

d.  Fourth  subtype,  the  Housefly. 

Internal  Anatomy  of  an  Insect.    (Exercise  4.) '. .  13 

Comparative  Study  of  the  Biting  and  Sucking  Lice.    (Exercise  5.) ....  14 

Biting  Lice  (Order  Mallophaga).    Anatomical  Study.    (Exercise  6a.) ..  15 

Biting  Lice  (Order  Mallophaga).    Systematic  Study.    (Exercise  6b.) ..  16 
The  Sucking  Lice  of  Mammals   (Family  Pediculidae).     Anatomical 

Study.    (Exercise  ya.) 16 

The  Sucking  Lice  (Family  Pediculidae).     Systematic  Study.     (Exer- 
cise yb.) 17 

The  Bedbug  (Family  Acanthiidae).    (Exercise  8a.) 18 

The  Cone-noses  (Family  Reduviidae).    (Exercise  8b.) 18 

The  Mosquitos  (Family  Culicidas).    (Exercise  9.) 19 

The  Buffalo  Gnats  (Family  Simuliidae).    (Exercise  loa.) 21 

The  Horseflies  (Family  Tabanidae).   Anatomical  Study.    (Exercise  lob.)  21 

The  Horseflies  (Family  Tabanidae).    Systematic  Study.    (Exercise  IDC.)  22 
The  Housefly  and  the  Stablefly  (Family  Muscidae).    A  Comparative 

Study.    (Exercise  n.) 22 

vii 


viii  CONTENTS 

PAGE 

The  Stablefly  and  the  Hornfly  (Family  Muscidae).     A  Comparative 

Study.    (Exercise  12.) 24 

The  Fleshflies  (Family  Sarcophagidse).    (Exercise  13.) 25 

The  Botflies  and  Warbleflies  (Family  (Estridae).    (Exercise  14.) 26 

The  Fleas  (Order  Siphonaptera).    Anatomical  Study.    (Exercise  isa.).  27 

The  Fleas  (Order  Siphonaptera).    Systematic  Study.    (Exercise  isb.).  28 

The  Louseflies  (Family  Hippoboscidae).    (Exercise  16.) 29 

The  Ticks  (Family  Ixodidae).    Anatomical  Study.    (Exercise  i7a.)  .  .  .  29 

The  Ticks  (Family  Ixodidas).    Systematic  Study.    (Exercise  lyb.).  ...  31 

The  Ticks  (Family  Ixodidae).    Other  Species.    (Exercise  i8a.) 31 

The  Ticks  (Family  Ixodidae).    Life  History  Study.    (Exercise  i8b.) ...  32 

The  Mites  (Family  Gamasidae).    (Exercise  iga.) 33 

The  Mites  (Family  Sarcoptidae).    (Exercise  i9b.) 34 

The  Mites  (Family  Sarcoptidae)  (cont.).     Psoroptic  species.     (Exercise 

20.) 34 

The  Insect  Sting.    (Exercise  2ia.) 35 

Venomous  Spiders  and  Scorpions.    (Exercise  2ib.) 36 

Parasiticides.    (Exercise  22.) 37 

The  Amoebae.    (Exercise  23a.) 40 

The  Trypanosoma.    (Exercise  23b.) 41 

The  Malaria  Parasites.    (Exercise  24.) 42 


PART  II 

HELMINTHOLOGY 

Introduction 45 

The  Roundworms  (Family  Ascaridae).    (Exercise  2$a.) 46 

Other  Ascaridae  (Oxyuris  and  Heterakis).    (Exercise  25b.) 48 

The  Thornheaded  Worms  (Class  Acanthocephala).    (Exercise  25c.) ...  48 

The  Hookworms  (Family  Strongylidae).    (Exercise  26.) 49 

The  Hookworms  (cont.).    (Family  Strongylidae).    (Exercise  27.) 50 

The  Lungworms  (Family  Strongylidae).    (Exercise  28.) 51 

The  Whip  worms  (Family  Trichotrachellidae).    (Exercise  293.) 52 

The  Trichina  (Family  Trichotrachellidae).    (Exercise  29b.) 53 

The  Filarise  (Family  Filariidae).    (Exercise  3oa.) 54 

The  Leeches  (Order  Hirudinea).    (Exercise  3ob.) 55 

The  Sheep  Liver  Fluke  (Family  Fasciolidae).    (Exercise  31.) 56 

Other  Trematodes.    (Exercise  32.) 58 

The  Tapeworms  (Class  Cestoda).    Morphological  Study.    (Exercise  33.)  59 

The  Tapeworms  (Class  Cestoda).    Systematic  Study.    (Exercise  34.) . .  61 


CONTENTS  ix 

PAGE 

Other  Tapeworms  (Class  Cestoda).    (Exercise  35.) 63 

Larval  Forms  of  Tapeworms.    (Exercise  36a.) 63 

Helminth  Ova.    (Exercise  360.) 65 

Insect  Larvae  (To  Distinguish  from  Worms).    (Exercise  37.) 65 

Anthehnintics.    (Exercise  38.) 66 

PART  III 

LIFE   HISTORY   STUDIES   ON   LIVING  PARASITES 

Introduction:  How  to  Proceed 69 

Life  History  of  the  common  Housefly.    (Exercise  39.) 70 

Life  History  of  the  Mosquito.    (Exercise  40.) 71 

Life  History  of  a  Flea.    (Exercise  41.) 72 


INTRODUCTION 

The  object  of  the  following  exercises  is  to  acquaint  the  stu- 
dent with  the  commoner  animal  parasites  of  man  and  of  the 
domesticated  animals,  including  insect  carriers  of  disease.  In 
studying  the  parasites  here  considered,  the  student  should 
bear  in  mind  the  following  statements  and  make  observations 
accordingly. 

A  parasite  can  only  be  a  parasite  as  it  lives  directly  at  the 
expense  of  another  organism,  whether  plant  or  animal.  This 
definition  leaves  few  if  any  animals  out  of  this  category,  inas- 
much as  the  dependence  of  animals  directly  upon  other  animals 
or  upon  plants  for  food  is  obvious.  But  if  we  restrict  this  mean- 
ing to  position,  living  in  or  upon  another  animal  or  plant  for 
purposes  of  feeding,  we  come  nearer  to  the  thought.  But  even 
here  there  are  many  organisms  which  live  in  or  upon  living 
animals  or  plants,  merely  sharing  their  food  with  them  without 
injuring  the  host.  This  we  call  commensalism.  Furthermore, 
organisms  feeding  in  or  upon  dead  bodies  would  not  be  termed 
parasites,  except  as  they  also  attack  or  feed  upon  living  tissue, 
as  occurs  in  certain  flesh  flies,  e.  g.  the  Texas  Screwworm  fly 
(Chrysomia  macellaria) ,  which  as  a  larva  may  feed  upon  the 
flesh  of  dead  or  living  animals.  Thus  our  definition  revolves 
about  the  idea  of  feeding  upon  living  organisms,  to  which 
should  be  added  that  the  host  must  not  be  killed  before  at 
least  the  developmental  period  or  larval  period  of  the  parasite 
is  completed,  otherwise  the  result  would  be  the  destruction 
of  the  parasite  as  well  as  the  host.  Parasitism  then  involves 
slow  death  to  the  host,  if  fatal  consequences  are  at  all  in- 
volved. The  definition  given  by  Braun  is,  viz.,  "By  the  term 
Parasites  is  understood  living  organisms  which  for  the  purpose 

ri 


xii  INTRODUCTION 

of  procuring  food,  take  up  their  abode  temporarily  or  perma- 
nently, on  or  within  other  living  organisms."  This  definition  will 
exclude  predaceous  animals  (Raubtiere),  which  capture  their 
prey  alive,  and  usually  kill  it  outright  for  purposes  of  food. 

Classes  of  parasites.  Other  than  the  two  general  classes, 
Ectoparasites  (external  parasites),  and  Entoparasites  (internal 
parasites),  all  parasites  may  be  placed  in  one  or  another  of  the 
following  divisions,  according  to  the  time  spent  in  or  upon  the 
host.  Facultative  parasites  have  the  power  of  changing  from  one 
host  to  another  of  a  different  species,  e.  g.  the  cat  and  dog  flea, 
Ctenocephalus  canis,  which  may  be  found  upon  the  cat,  the 
dog,  the  rat  and  man;  the  rat  flea,  Ceratophyllus  fasciatus,  upon 
the  rat  and  upon  man;  the  wood  tick,  Dermacentor  variabilis, 
may  be  found  on  nearly  all  species  of  domesticated  animals  and 
man.  Obligatory  parasites  are  restricted  to  one  species  of  host, 
e.  g.  the  biting  bird  lice  (Mallophaga),  which  perish  sooner  or 
later  if  transferred  to  another  species  of  host.  Intermittent  par- 
asites are  such  as  prey  upon  the  host  for  food,  as  in  the  female 
horseflies  (Tabanidae)  attacking  horses  and  cattle  for  the  pur- 
pose of  sucking  blood  and  leaving  the  host  after  a  meal.  Tran- 
sitory parasites  are  such  as  pass  part  of  the  life  history  at  the 
expense  of  the  host,  for  example,  the  botflies  (CEstridae)  which 
pass  the  larval  period  of  development  within  the  body  of  the 
host,  while  the  adult  botflies  are  free  living  and  do  not  attack 
other  animals  for  food. 

Effect  of  parasitism  on  the  host.  That  an  animal  is  para- 
sitized does  not  necessarily  involve  it  in  death,  not  even  in  great 
inconvenience,  although  the  parasite  is  actually  living  at  its 
expense.  The  presence  of  a  few  bots  in  the  stomach  of  a  horse 
may  not  affect  that  animal  in  the  least,  nor  would  the  presence 
of  a  few  lice  on  the  body  of  an  animal,  but  with  the  multiplica- 
tion of  these  parasites  there  will  be  increased  inconvenience  to 
both  hosts.  The  presence  of  a  few  maggots  in  the  fleshy  part  of 
a  sheep's  leg  might  cause  little  damage,  but  let  these  be  in  the 
nasal  sinuses  or  at  the  base  of  the  brain,  and  the  gravity  of  the 


-       INTRODUCTION  xiii 

situation  will  be  greatly  augmented.  Thus  the  effect  of  parasi- 
tism on  the  host  depends  both  on  the  number  and  position  of 
the  parasite. 

Effect  of  parasitism  on  the  parasite.  All  parasites  are 
more  or  less  specialized  in  the  direction  of  their  habits,  e.  g.  fleas 
are  laterally  compressed  to  effect  ease  of  motion  between  hairs; 
lice  are  horizontally  flattened  and  are  provided  with  strong 
clasping  organs  to  hold  fast  to  hairs,  and  both  of  these  examples 
are  wingless  and  have  sacrificed  much  of  the  ordinary  means  of 
locomotion.  Entoparasites  are  usually  provided  with  special- 
ized hooks,  barbs,  suckers,  etc.,  for  purposes  of  attachment  to 
the  alimentary  canal  or  other  organs,  e.  g.  the  botfly  larvae, 
and  among  the  Helminths,  the  flukes  (Trematoda),  the  tape- 
worms (Cestoda),  etc.  Perhaps  because  of  the  ease  in  securing 
food  the  sense  organs  are  usually  not  strongly  developed,  the 
eyes  may  be  wanting  or  very  simple.  The  mouthparts  differ  in 
the  several  groups,  depending  on  their  special  adaptation  of 
habit.  It  is  interesting  to  note  that  the  parasitic  habit  has  re- 
sulted in  the  development  of  structural  similarity.  This  is 
especially  prominent  in  the  clasping  structures  of  the  biting  and 
sucking  lice,  which  belong  systematically  to  two  different  orders, 
namely,  the  Mallophaga  and  the  Hemiptera. 

Origin  of  parasitism.  Modern  parasites  are  restricted 
more  or  less  completely  to  a  particular  host  animal,  which  would 
necessitate  the  deduction  that  the  parasite  must  have  developed 
its  habit  after  the  existence  of  the  host,  and  in  consequence  that 
parasitism  must  be  a  recently  acquired  habit.  This  thought  is 
further  expressed  by  the  study  of  the  life  history  of  the  parasite. 
Invariably  the  earlier  stages  point  to  a  free  living  existence. 
Perhaps  the  ancestors  of  a  given  group  of  modern  parasites  were 
attracted  to  the  waste  food,  offal  and  exudations  of  certain 
animals;  the  search  for  food  may  have  become  simplified;  they 
began  living  as  messmates  or  commensalists,  or  as  scavengers; 
the  association  between  the  species  may  have  become  closer  and 
the  eventual  line  of  parasitism  completed.  This  is  also  borne 


xiv  INTRODUCTION 

out  by  a  study  of  the  nearest  allies  of  a  given  parasite  and  mem- 
bers of  a  given  family  of  parasites,  in  which  the  gradation  from 
free  living  animal  to  parasite  may  often  be  traced.  Among  the 
biting  lice  (Mallophaga)  there  are  species  which  have  the  power 
of  running  freely,  e.  g.  Menopon  pallidum,  the  common  hen 
louse,  which  may  live  for  a  considerable  length  of  time  off  its 
host,  while  other  species  have  become  quite  sessile,  as  in  the  case 
of  the  worm-like  louse  Menopon  titan,  which  inhabits  the  pouch 
of  the  pelican.  Among  the  fleas  there  are  also  good  examples 
of  this  gradation  in  habit  and  structure,  e.  g.  the  human  flea, 
Pulex  irritans,  while  it  has  developed  the  springing  power,  is 
comparatively  free  to  move  from  place  to  place,  while  the  hen 
flea,  Xestopsylla  gallina,  is  quite  sessile  and  holds  fast  at  one 
point  to  draw  blood  much  like  a  tick. 

The  ectoparasites  will  be  studied  first,  on  account  of  the 
greater  ease  of  handling  them.  In  the  meantime  the  student 
will  gain  greater  efficiency,  preparatory  to  studying  the  more 
difficult  entoparasites. 

DIRECTIONS 

The  student  should  provide  himself  with  a  hand  lens  and 
loose  leaf  drawing  paper  and  notebook. 

Drawings  should  be  made  with  a  hard  pencil,  preferably  3H. 
Do  not  use  a  fountain  pen  or  soft  pencil  for  this  work. 

Notes  should  be  taken  on  each  exercise  and  properly  inter- 
leaved. 

Each  exercise  will  provide  enough  material  for  a  laboratory 
session  of  from  2^2  to  3  hours. 

Specimens,  whether  mounted  dry,  on  slides  or  otherwise 
prepared  must  be  handled  with  care. 

Special  care  must  be  exercised  in  studying  microscopic  slides 
under  the  compound  microscope.  Do  not  crush  the  specimen 
by  running  the  objective  down  upon  it. 


INTRODUCTION  xv 

SUGGESTIONS 

Students  are  strongly  urged  to  be  on  the  "lookout"  for  cases 
of  parasitism,  not  only  because  this  lends  emphasis  to  the  work 
in  hand,  but  also  because  of  the  scientific  importance  and  value 
of  such  observations  and  collections. 

Internal  parasites  (taken  wet)  such  as  tapeworms,  round- 
worms,  bots,  warbles,  etc.,  may  be  preserved  in  75%  alcohol  or 
4%  formaldehyde,  preferably  the  latter.  If  alcohol  is  used  as  a 
preservative  the  specimens  should  be  run  into  the  higher  grades 
of  alcohol  gradually,  beginning  with  25%  and  allowing  2  or  3 
hours  between  each  change  (25%,  35%,  50%,  75%). 

Insect  specimens  may  be  mounted  on  pins  or  points  or  may 
also  be  preserved  as  above. 


PARASITOLOGY 


PARASITOLOGY 

PART  I 
MEDICAL  ENTOMOLOGY 

INSECTS  AND  DISEASE 

DISCUSSION 
HOW  PATHOLOGICAL  CONDITIONS  ARE  PRODUCED 

General  considerations.  By  pathological  conditions  we 
would  have  understood  a  diseased  state  of  tissue,  deranged 
function  or  the  like, — an  abnormal  condition  of  the  body.  Ani- 
mal diseases  may  be  produced  in  many  ways,  and  it  is  not  the 
object  of  this  exercise  to  give  a  complete  discussion  of  even  the 
general  principles  of  pathology,  except  only  in  so  far  as  insects 
are  concerned.  In  this  work  we  cannot  merely  define  those  in- 
sects as  parasites  in  the  usual  acceptance  of  the  term  as  defined 
by  Braun,  "living  organisms  which  take  up  their  abode,  for  the 
purpose  of  procuring  food,  temporarily  or  permanently,  on  or 
within  other  living  organisms,"  because  there  are  certain  insects 
which  are  not  usually  considered  as  parasites,  but  are  never- 
theless the  grossest  transmitters  of  diseases,  e.  g.  the  housefly, 
as  a  transmitter  of  certain  enteric  affections. 

Insects  and  arachnids  may  relate  to  pathological  conditions, 
whether  serious  or  of  little  consequence,  in  one  or  more  of  the 
following  ways,  first,  through  direct  infection,  second,  through 


2  :  M^DIC&L  ENTOMOLOGY 

indirect  infection,  third,  through  internal  parasitism,  fourth, 
through  external  parasitism,  and  lastly,  through  insect  venoms. 
The  same  species  may  fall  as  legitimately  into  two  divisions,  as, 
for  example,  the  Texas  fever  tick,  which  if  not  infected  with  the 
causative  organisms  of  the  fever  need  only  be  considered  as  an 
external  parasite,  but  when  the  causative  fever  organisms  are 
present  in  the  tick  would  relate  it  also  to  direct  infection. 

Direct  infection.  Direct  infection  under  ordinary  conditions 
can  only  be  produced  by  an  insect  or  arachnid  possessing  pierc- 
ing mouthparts,  and  here  no  special  order  or  larger  group  can 
well  be  referred  to,  inasmuch  as  closely  related  insects  may  have 
very  different  mouth  structures.  The  common  housefly  and  the 
stable  fly,  for  example,  belong  to  the  same  family,  therefore  are 
closely  related,  yet  have  very  different  mouthparts;  though  both 
are  suctorial,  the  former  is  unable  to  pierce  the  skin,  whereas  the 
latter  can  do  so  with  ease. 

By  direct  infection  is  meant  the  introduction  of  a  pathogenic 
organism,  whether  bacterial  or  protozoan,  into  the  circulation 
of  a  higher  animal.  The  Anopheles  mosquito  is  thus  related  to 
this  manner  of  transmission,  since  this  insect  introduces  the 
malaria  parasite  directly  into  the  blood  stream  of  man.  The 
same  is  true  of  the  Stegomyia  mosquito  and  yellow  fever,  the 
Glossina  flies  and  sleeping  sickness,  the  horseflies  and  anthrax, 
the  Texas  fever  tick  and  Texas  fever,  etc.  Direct  infectors  are 
usually  temporary  ectoparasites  (intermittent  parasites),  per- 
mitting transfer  of  activity  from  animal  to  animal. 

While  the  conditions  just  discussed  are  to  be  referred  to  direct 
infection,  there  is  still  a  possibility  for  an  insect  with  mandibu- 
late  mouthparts  or  with  haustellate  mouthparts  of  non-piercing 
form  to  infect  an  animal  as  directly  as  one  possessing  piercing 
mouthparts.  Thus  the  housefly  may,  by  means  of  mouthparts 
and  foot  structures,  transmit  gangrene  from  an  animal  thus 
affected  to  an  animal  undergoing  surgical  operation,  or  suffering 
from  an  open  wound.  Pustular  matter  might  be  transmitted 
in  an  equally  direct  manner. 


INSECTS  AND  DISEASE  3 

Indirect  infection.  This  form  of  infection  relates  chiefly  to 
enteric  diseases  in  the  causation  of  which  the  pathogenic  organism 
is  deposited  upon  the  food  of  the  higher  animal  by  the  insect. 
Thus  the  food  is  first  infected,  and  through  this  the  pathogenic 
organism  is  implanted  within  the  alimentary  canal  of  the  victim; 
in  this  way  the  insect  is  concerned  only  indirectly.  The  housefly 
which  is  quite  certainly  one  of  the  grossest  transmitters  of 
enteric  diseases  is  so  only  because  of  accident  of  habit  and  struc- 
ture, feeding  as  it  does  indiscriminately  upon  excrement  and 
upon  the  food  of  higher  animals.  The  structure  of  the  proboscis 
and  feet  is  such  as  to  make  it  quite  difficult  not  to  carry  particles 
of  the  excrement  to  the  food.  Thus  if  disease  producing  "  germs ' ' 
are  present  the  result  is  inevitable. 

Insects  possessing  mouthparts  not  adapted  to  piercing  the 
skin  (whether  biting  or  sucking)  can  relate  only  to  this  form  of 
infection,  and  indeed  any  insect  or  arachnid  may  be  an  indirect 
carrier  by  accident.  Furthermore  insects  ordinarily  relating 
only  to  indirect  infection  may  produce  direct  infection  of  certain 
kinds,  where  there  is  access  to  an  open  wound;  for  example,  the 
transmission  of  gangrene  through  the  agency  of  the  common 
housefly  from  a  diseased  animal  to  another  animal  which  presents 
an  open  wound,  cut  or  sore. 

Internal  parasitism.  There  are  no  insects  as  far  as  is  known 
which  spend  their  entire  life  history  in  the  form  of  internal 
parasites.  There  are,  however,  a  number  which  pass  their  larval 
period  (period  of  growth)  within  the  alimentary  canal  or  in  the 
muscle  tissue  of  higher  animals.  The  best  known  representatives 
of  this  group  are  the  botflies  and  the  warble  flies,  the  former 
found  mainly  in  the  stomach  of  equine  animals,  while  the  latter 
are  found  in  the  muscle  tissue  of  bovine  and  equine  animals, 
rodents  and  sometimes  man.  The  damage  done  by  internal 
parasites  is  of  various  kinds;  first,  disturbed  nutrition,  and 
secondly,  irritation  caused  by  the  burrowing  parasites  in  the 
muscles  or  by  the  attachment  of  hooks  to  the  intestinal  lining 
for  the  purpose  of  prehension. 


4  MEDICAL  ENTOMOLOGY 

External  parasitism.  The  most  important  and  most  abun- 
dant external  parasites  of  man  and  of  the  domesticated  animals 
are  found  among  the  insects  and  arachnids.  Very  serious  and 
often  fatal  results  are  due  to  this  form  of  irritation,  and  the  loss 
of  blood  due  to  an  abundance  of  any  blood-sucking  species  must 
not  be  overlooked.  External  parasites  may  be  either  permanent 
or  temporary  with  relation  to  their  host.  The  commonest 
permanent  parasites  are  the  biting  and  sucking  lice,  which  are 
usually  transferred  from  host  to  host  by  close  association  of 
mammals  while  sleeping  together,  or  in  close  quarters  or  in 
copulation;  in  poultry  generally  while  roosting.  While  per- 
manent ectoparasites  are  not  so  largely  concerned  in  the  direct 
transmission  of  infectious  diseases,  certain  sucking  lice  are 
known  to  be  agents  in  the  transmission  of  Trypanosomes.  The 
temporary  (intermittent)  ectoparasites  are  the  most  important 
of  all  disease  carriers,  on  account  of  their  change  of  host,  drop- 
ping off  or  flying  away  from  one  animal  to  another  of  the  same 
or  a  different  species.  It  may  well  be  seen  that  herein  lies  the 
danger  of  transmitting  infectious  diseases  from  animal  to 
animal.  The  temporary  ectoparasites  are  well  represented  by 
the  fleas,  bedbugs  and  ticks. 

Insect  venoms.  Another  form  of  irritation  is  produced  by 
the  inoculation  of  a  specific  poison  into  a  wound  produced  by  a 
piercing  or  stinging  insect.  Many  insects  produce  severe  irrita- 
tions by  their  bites,  which  fact  can  be  accounted  for  by  the 
presence  of  a  venom-secreting  gland,  often  salivary.  The  cone- 
noses  or  kissing  bugs  (Reduviidae)  inflict  a  very  painful  wound 
which  is  aggravated  by  a  poison;  other  insects  produce  nettling 
when  handled,  e.  g.  the  blister  beetles  (Meloidae).  Again,  the 
familiar  sting  of  the  bee  and  the  wasp  is  chiefly  painful  because 
of  the  injection  of  a  specific  poison. 


INSECTS  AND  DISEASE  5 

HOW  INSECTS  CARRY  DISEASE 

In  the  above  section  we  have  seen  how  insects  relate  to  the 
causation  of  disease.  It  is  obvious  that  we  may  view  the  field 
from  a  slightly  different  angle,  i.  e.  our  classification  may  be 
based  on  transmission  as  well. 

The  simplest  way  in  which  insects  enter  in  as  a  factor  in  the 
transmission  of  disease  is  through  soiled  feet  and  mouthparts. 
Any  insect  might  accidentally  become  contaminated  with  infec- 
tive sputum  or  fecal  matter  and  in  turn  might  accidentally  come 
in  contact  with  human  foods,  thus  becoming  an  indirect  infector, 
as  already  explained.  In  this  connection  the  normal  habit  of 
the  insect  must  be  considered,  i.  e.  its  breeding  habits,  food 
habits  and  general  behavior.  Thus  the  housefly  enters  in  as  a 
factor  in  the  transmission  of  such  diseases  as  typhoid  fever  and 
tuberculosis,  because  of  its  normal  habits  and  is  a  carrier  in  the 
simplest  possible  manner. 

A  second  purely  mechanical  method  of  transmission,  though 
more  restricted,  is  by  means  of  a  soiled  piercing  proboscis,  in  cases 
of  certain  blood  diseases.  In  the  foregoing  class  the  type  of 
mouthparts  does  not  enter  as  a  restrictive  factor,  but  in  order 
that  the  proboscis  may  become  soiled  with  blood  the  mouthparts 
must  be  capable  of  piercing  the  skin,  thus  coming  in  contact 
with  the  blood  and  its  contained  parasites,  if  present.  The 
inoculation  of  the  second  host  may  be  purely  mechanical.  In- 
sects that  belong  to  this  class  of  carriers  ordinarily  have  heavy 
piercing  mouthparts  drawing  considerable  blood,  are  inter- 
mittent parasites,  and  often  go  from  host  to  host  within  a  short 
time.  The  horsefly  (Tabanus)  is  a  good  representative  of  this 
class  in  its  chance  relation  to  anthrax. 

A  still  more  highly  specialized  method  is  involved  in  the  trans- 
mission of  bubonic  plague  by  fleas.  In  this  case  the  carrier  has 
piercing  mouthparts,  is  bloodsucking  and  an  intermittent  para- 
site, but  it  does  not  inoculate  the  second  host  by  means  of  a 
soiled  proboscis  as  far  as  is  known.  The  plague  bacilli  when 


6  MEDICAL  ENTOMOLOGY 

taken  into  the  stomach  of  the  flea  increase  in  numbers  and  do 
not  become  attenuated,  but  pass  out  with  the  feces  or  even  in 
undigested  blood  per  anum  in  a  virulent  condition;  the  direct 
inoculation  must  be  through  a  "rubbing  in"  process  onthe  part 
of  either  the  host  or  the  flea.  ^K: 

The  greatest  complexity  is  involved  in  such  cases  in  which  the 
carrier  is  a  necessary  factor  in  the  life  history  of  the  pathogenic 
organism,  e.  g.  the  Anopheles  mosquito  has  piercing  mouthparts, 
is  bloodsucking,  and  an  intermittent  parasite,  in  which  a  given 
period  of  time  must  elapse  before  it  can  transmit  the  causative 
organism  of  malaria,  once  it  has  become  infected.  This  period 
of  time  corresponds  to  the  time  required  for  the  Plasmodium  to 
pass  through  its  sexual  cycle  and  find  its  way  back  into  the 
proboscis,  i.  e.  into  the  salivary  glands,  ready  to  be  reinoculated. 

INSECT  MOUTHPARTS 

Importance  of  mouthparts.  It  becomes  evident  that  an 
insect  possessing  mouthparts  capable  of  piercing  the  skin  of  the 
higher  animals  must  be  looked  upon  as  a  possible  carrier  of 
blood  infection,  although  it  may  in  actual  experience  never 
attack  other  animals.  If  the  insect  is  provided  with  mouthparts 
of  the  usual  biting  type  it  cannot  relate  to  infection  introduced 
through  the  circulation  except  by  rare  accident  through  a  pre- 
^fcwisly  inflicted  open  wound. 

The  mosquito  would  be  harmless  as  far  as  malaria  and  yellow 
fever  are  concerned  if  the  mouthparts  were  of  the  mandibulate 
or  biting  type.  These  insects  together  with  certain  other  species 
such  as  the  stablefly,  Stomoxys  calcitrans,  the  tsetse  flies  and  the 
ticks  are  important  because  of  the  power  which  they  possess  of 
piercing  the  skin  of  higher  animals  and  introducing  parasitic 
organisms  into  the  blood.  The  housefly  on  the  other  hand  cannot 
introduce  organisms  directly  into  tjie  circulation  because  its 
mouthparts  are  not  of  the  piercing  type.  These  creatures  are 
attracted  by  and  often  breed  in  excrementous  matter,  are  then 


INSECTS  AND  DISEASE  7 

attracted  to  the  food  of  human  beings,  and  introduce  thereon 
the  pathogenic  organisms  from  their  mouthparts  and  feet. 

The  actual  measures  of  control  are  quite  often  dependent  on  a 
knowledge  of  the  mouthparts  of  the  insect  concerned. 

Inadequacy  of  old  systems.  In  the  study  of  Medical  Ento- 
mology it  is  no  longer  sufficient  to  divide  the  insects  into  only 
two  groups  as  based  on  the  mouthparts,  namely,  Mandibulate, 
or  biting,  and  Haustellate,  or  sucking.  This  fact  becomes 
clearer  when  it  is  considered  that  the  housefly  (Musca  domestica) 
and  the  stablefly  (Stomoxys  calcitrans)  both  have  sucking 
mouthparts  and  belong  to  the  same  family,  Muscidae,  hence 
are  systematically  very  closely  related,  yet  from  the  standpoint 
of  disease  transmission  are  widely  different.  By  virtue  of  the 
piercing  structures  composing  the  mouthparts  of  the  stablefly  it 
relates  to  direct  infection,  while  the  housefly's  proboscis,  quite 
ineffective  as  a  piercing  structure,  relates  it  to  indirect  infection, 
— not  however  of  less  importance  as  a  disease  transmitter. 

Because  of  the  deficiency  of  the  older  systems  of  mouthpart 
classification  the  following  types  will  be  considered. 

Types  of  insect  mouthparts.  The  following  types  of  mouth- 
parts  may  be  recognized: 

1.  Orthopteron  type, — biting  or  chewing  structures,  as  in  the 
grasshopper. 

2.  Physopodan  type, — transitional  mouthparts  of  biting  form 
but  functionally  serving  as  suctorial  organs,  as  in  the  thrips.   • 

3.  Eemipteron  type, — suctorial  organs  enclosing  three  or  four 
piercing  setae  closely  ensheathed  within  the  labiurn,  as  in  the 
cone-noses. 

4.  Dipteron  type, — suctorial  organs;  no  special  example  being 
available  for  the  entire  order,  the  following  subtypes  must  be 
recognized: 

A.  First    subtype — Mosquito,    loosely   ensheathed   piercing 
bristle-like  structures,  six  in  number. 

B.  Second  subtype — Horsefly,  piercing  blade-like  structures, 
six  in  number,  loosely  ensheathed. 


8  MEDICAL  ENTOMOLOGY 

C.  Third  subtype — Stablefly,  closely  ensheathed  heavy  pierc- 
ing structures,  two  in  number. 

D.  Fourth  subtype — Housefly,  suctorial  muscular  proboscis, 
but  not  suited  to  piercing. 

5.  Hymenopteron  type — suctorial,  lapping  form,  as  in   the 
honeybee  and  ant,  mandibles  modified  for  portage  and  combat. 

6.  Lepidopteron  type — suctorial,  coiled  tube  form,  as  in  the 
cabbage  butterfly. 

EXERCISE  1 

A  STUDY  OF  INSECT  MOUTHPARTS 

A.  Orthopteron  type. 

To  illustrate  this  type  either  the  grasshopper  or  the  cockroach 
may  be  used,  but  since  the  former  is  more  easily  obtainable  and 
can  be  handled  more  satisfactorily  it  will  serve  this  purpose  very 
well.  This  type,  the  mandibulate  or  biting,  is  the  generalized  or 
primitive  form,  and  will  serve  as  a  basis  for  later  comparisons 
and  derivations. 

If  the  head  of  the  grasshopper  is  viewed  from  the  side  and 
again  from  the  front  the  relative  position  of  the  parts  will  be 
better  understood. 

Separating  the  structures  composing  the  mouth  of  the  grass- 
hopper, the  following  pieces  will  be  observed.  In  front,  low 
down  on  the  head,  hangs  the  labrum,  or  upper  lip,  attached  to 
the  clypeus,  easily  lifted  as  one  would  raise  a  hinged  lid,  the 
hinge  line  being  at  the  lower  part  of  the  sclerite  known  as  the 
clypeus. 

The  labrum  functions  as  does  the  upper  lip  in  higher  animals, 
in  that  it  draws  the  food  toward  the  mandibles.  In  this  the 
labrum  is  greatly  aided  by  a  rough  toothed  structure  called  the 
epipharynx,  which  forms  the  inner  lining  of  the  labrum  and  the 
clypeus.  Because  of  the  close  association  of  these  two  structures 
they  are  often  referred  to  as  a  double  organ,  the  labrum-epi- 


A  STUDY  OF  INSECT  MOUTHPARTS  9 

pharynx.  Removing  the  labrum  the  pair  of  heavy  black  oppos- 
able  jaws,  or  mandibles,  is  exposed.  These  are  biting  structures 
par  excellence.  They  are  toothed  and  movable  laterally,  in- 
stead of  vertically  as  in  the  vertebrates.  Dislodging  the  man- 
dibles brings  the  pair  of  maxilla,  or  accessory  jaws,  into  view. 
These  organs  are  also  called^/  maxilla.  These  are  composite 
structures,  each  separable  into  lacinia,  galea,  palpus,  cardo  and 
stipes,  which  should  be  carefully  noted,  inasmuch  as  they  undergo 
great  modification  in  the  remaining  types  of  mouthparts.  The 
two  supporting  sclerites  are  called  the  cardo  (basal),  and  stipes 
(the  second)  while  the  distal  lobes  are  called,  i,  the  maxillary 
palpus  (a  jointed  structure),  2,  the  galea  (median  and  fleshy), 
3,  the  lacinia  (inner  and  toothed,  capable  of  aiding  in  comminut- 
ing food). 

Underneath  the  maxillae  and  forming  the  floor  of  the  mouth, 
lies  the  lower  lip,  or  labium,  a  double  structure,  frequently  called 
the  second  maxilla.  On  the  same  plan  as  the  maxillae,  the 
labium  consists  of  a  basal  sclerite,  the  submentum,  followed  by 
the  mentum,  upon  which  rest  the  labial  palpi  (a  pair  of  outer, 
jointed  structures,  to  the  right  and  left)  and  the  lignite  (a  pair 
of  straplike  pieces  which  together  correspond  to  the  upper  lip). 
The  labium  is,  like  the  maxillae,  also  subject  to  much  modifica- 
tion. 

The  fleshy  organ  still  remaining  in  the  mouth  cavity  after  the 
parts  just  described  have  been  removed,  is  the  tongue,  or  hypo- 
pharynx,  functionally  comparable  to  the  tongue  of  vertebrates, 
an  organ  of  taste. 

Draw  side  and  front  view  of  grasshopper's  head;  also  make  a 
drawing  of  each  mouthpart  separately,  labelling  all  parts. 

B.  Hymenopteron  type. 

In  this  type  the  two  general  classes  of  mouth  structures,  the 
Mandibulate  and  Haustellate,  find  a  rather  strong  development 
in  the  same  species,  though  the  former  structures  are  not  con- 
cerned as  comminuting  organs  with  respect  to  food.  The  honey- 


io  MEDICAL  ENTOMOLOGY 

bee  will  serve  as  a  representative  species.  Examine  mounted 
specimens  of  mouthparts  as  well  as  complete  heads.  The 
labrum,  above,  is  narrow  and  quite  simple.  The  mandibles  are 
easily  distinguishable  and  are  useful  wax  implements.  In  ants 
the  mandibles  are  highly  efficient  carrying  organs  and  weapons 
of  defense.  The  maxilla  form  the  lateral  conspicuous  wings  of 
the  suctorial  parts;  the  lacinia  and  galea  are  fused  into  one 
piece,  and  the  maxillary  palpi  are  quite  minute.  The  labium  is 
represented  by  the  long  structures  to  the  right  and  left  of  the 
middle  tube,  which  is  probably  the  hypopharynx.  The  hypo- 
pharynx  terminates  in  a  spoon  or  bouton,  which  completes  the 
lapping  character  of  the  type. 
Draw  and  label  parts. 


EXERCISE  2 

INSECT  MOUTHPARTS  (cont.) 

C.  Hemipteron  type. 

A  very  different  sort  of  organ  than  the  above  described  types 
is  found  in  the  Hemiptera.  Here  the  labium  forms  a  prominent 
beak,  which  is  usually  three  (rarely  one  or  four),  jointed,  and 
telescopic.  Examine  mounted  specimens  of  mouthparts  of  a 
cone-nose, — Reduviidae.  The  beak  encloses  a  pair  of  mandibles, 
often  provided  with  cruel  barbs  at  the  distal  end,  and  the 
maxilla,  all  bristle-like,  and  of  great  efficiency  in  piercing  the 
skin.  The  maxillae  are  more  or  less  completely  joined,  forming 
a  tube,  so  that  often  only  three  bristles  or  stylets  can  be  seen  on 
examination.  The  labrum  is  quite  short  and  inconspicuous. 

Draw  side  views  of  the  head  of  the  cone-nose,  showing  the 
proboscis  and  stylets.  Label  the  parts. 

D.  Lepidopteron  type. 

This  type,  represented  by  the  commoner  butterflies  and  moths, 
is  typically  a  coiled,  sucking  tube,  capable  of  great  elongation. 


A  STUDY  OF  INSECT  MOUTHPARTS  n 

Taking  the  cabbage  butterfly  (Pieris  rapa)  as  an  example,  the 
labrum  is  seen  to  be  greatly  reduced,  the  mandibles  absent.  The 
mandibles  may  be  weakly  present  in  the  lower  Lepidoptera. 
The  maxillae  are  apparently  only  represented  by  the  galea, 
which  by  the  close  approximation  of  their  inner  grooved  surfaces 
form  the  proboscis,  long  and  coiled.  The  double  structure  of  the 
proboscis  can  easily  be  demonstrated  by  manipulation.  The 
labium  is  represented  by  the  labial  palpi. 
Draw  and  label  parts. 

E.  Dipteron  type. 

a.  First  subtype,  the  mosquito.  The  more  generalized  type 
of  Dipteron  mouthparts  is  found  in  the  mosquito,  hence  here  we 
find  the  maximum  number  of  stylets  or  bristles,  representing  the 
parts  of  the  more  generalized  types,  loosely  ensheathed  in  the 
elongated  labium,  the  whole  forming  the  prominent  beak,  or 
proboscis.  The  identity  of  the  six  stylets  is  not  well  established, 
though  it  is  generally  accepted  that  they  represent  the  two 
mandibles,  the  two  maxilla  (distinctly  serrated  distally),  the 
hypopharynx,  and  the  labrum.  The  palpi  are  conspicuous  struc- 
tures in  all  mosquitoes,  and  are  useful  as  a  means  for  classifica- 
tion. These  represent  the  maxillary  palpi  of  the  grasshopper 
while  the  pair  of  flattened  lobe-like  organs  forming  the  distal 
portion  of  the  proboscis  are  said  to  represent  the  labial  palpi, 
and  are  called  the  lobelia. 

Draw  and  label  parts. 


EXERCISE  3 

INSECT  MOUTHPARTS  (cont.) 

E.  Dipteron  type  (cont.). 

b.  Second  subtype — the  horsefly.  While  retaining  the  same 
number  of  parts  as  in  the  mosquito,  this  subtype  is  distinctly 
characterized  by  the  flattened  blade-like  condition  of  these 


12  MEDICAL  ENTOMOLOGY 

organs,  rather  than  the  bristle-like  or  stylet  form  of  the  first 
subtype.  That  these  mouthparts  serve  quite  largely  as  cutting 
structures  is  evident  from  the  large  wound  made  and  the  quan- 
tity of  blood  drawn  by  the  "bite"  of  a  horsefly,  especially  one  of 
the  larger  species,  such  as  the  black  horsefly  (Tabanus  atratus). 
The  labium  is  the  conspicuous  median  portion,  loosely  ensheath- 
ing  the  blades,  and  terminating  in  large  lobelia.  The  mandibles 
are  distinctly  flattened  and  sabre-like,  while  the  maxilla  are 
narrower  and  provided  with  conspicuous  palpi.  The  hypo- 
pharynx  and  labrum-epipharynx  are  both  lancet-like.  In  the 
male  these  piercing  parts  are  very  weakly  developed,  and  are  not 
useful  as  weapons  of  attack. 
Draw  and  label  parts. 

c.  Third  subtype — the  stablefiy.    This  subtype  represents  a 
group  of  piercing  flies  in  which  the  mouthparts  are  distinctly 
specialized,  and  show,  together  with  the  next  subtype,  to  what 
extent  these  structures  may  become  differentiated  within  the 
same  family  of  insects. 

The  proboscis  at  rest  is  carried  at  the  position  of  a  bayonet 
at  charge,  and  is  therefore  provided  with  a  prominent  knee  or 
elbow,  which  portion  is  highly  muscular.  This  conspicuous 
organ  is  the  labium,  terminating  in  the  labella,  which  are  pro- 
vided with  a  complex  series  of  cutting  and  adhesive  structures. 
Within  the  folds  of  the  labium  and  easily  removable  through 
the  upper  groove  lie  two  sharp,  heavy,  bristle-like  structures, 
the  labrum,  the  uppermost  and  heavier  stylet,  and  the  hypo- 
pharynx,  a  lower  and  weaker  structure,  the  two  forming,  as 
in  other  Muscidae,  a  sucking  tube  supported  within  the  folds 
of  the  labium.  The  maxillary  palpi  are  less  prominent  than  in 
the  other  Muscidae,  but  are  similarly  located,  at  the  proximal 
end  of  the  proboscis. 

Draw  and  label  parts. 

d.  Fourth  subtype — the  housefly.    Here  the  prominent  fleshy 
proboscis  consists  mainly  of  the  labium,  which  terminates  in  a 
pair  of  corrugated  rasping  organs,  the  labella,  and  is  attached  in 


INTERNAL  ANATOMY  OF  AN  INSECT  13 

knee-like  form  to  the  elongated  head.  The  entire  mass  is  highly 
muscular,  and  may  either  be  protruded,  as  in  feeding,  or  quite 
largely  withdrawn,  while  at  rest.  Lying  on  top  of  the  grooved 
labium  is  the  inconspicuous  prolonged  spade-like  labrum,  which 
forms  with  the  hypopharynx  a  sucking  tube,  supported  by  the 
labium,  which  latter  also  encloses  the  salivary  canal.  By  an 
examination  of  the  labrum  it  will  be  seen  that  it  forms  a  kind  of 
convex  cover  to  the  concaved  hypopharynx,  thus  giving  rise  to 
a  food  tube.  The  maxillae  have  evidently  become  fused  with 
the  fleshy  knee  of  the  proboscis,  and  only  the  prominent  max- 
illary palpi  remain. 
Draw  and  label  parts. 

EXERCISE  4 

INTERNAL  ANATOMY  OF  AN  INSECT 

It  is  important  that  the  student  familiarize  himself  with  the 
internal  anatomy  of  an  insect,  with  special  reference  to  the  di- 
gestive system  and  its  accessory  structures,  such  as  the  salivary 
glands.  For  this  purpose  a  grasshopper  is  to  be  dissected,  ow- 
ing to  ease  of  manipulation.  If  the  student  has  time  it  is  recom- 
mended that  the  internal  anatomy  of  a  stablefly  be  studied  for 
the  sake  of  comparison. 

With  fine  pointed  needles  or  scissors  open  the  dorsal  abdominal 
wall,  separating  the  right  and  left  sides  to  expose  the  intestine. 
Small  pins  will  be  found  convenient  to  pin  down  the  parts  and 
thus  allow  more  freedom  in  working.  The  insect  should  be 
dissected  under  water  in  a  dish  with  a  paraffin  floor. 

A.  Determine  the  following  parts,  drawing  and  labelling  the 
same. 

a.  The  mouthparts,  without  reference  at  this  time  to  details; 
these  have  already  been  studied. 

b.  The  oesophagus,  a  straight  tube  leading  from  the  pharynx 
to  the  crop. 


I4  MEDICAL  ENTOMOLOGY 

c.  The   opening   of  the   salivary  ducts,   emptying  into  the 
oesophagus,  and  the  pair  of  salivary  glands. 

d.  The  crop,  or  short  food-receiving  chamber,  emptying  into 
the  stomach  proper,  a  longer  cylindrical  chamber,  anterior  to 
which  are  the  gastric  caeca,  and  posterior  the  hair-like  malphigian 
tubules. 

e.  The  intestine,  a  long,  slender,  coiled  tube  posterior  to 
the  stomach,  consisting  of  three  parts,  the  ileum,  colon  and 
rectum,  the  latter  a  short  straight  tube  ending  in  the  anus. 

B.  If  time  remains  the  student  is  urged  to  study  the  internal 
anatomy  of  a  stablefly  for  purposes  of  comparison. 

a.  Note  the  connection  between  the  blood-sucking  proboscis 
and  the  oesophagus.        x 

b.  How  does  the  crop  compare  with  the  crop  of  the  grass- 
hopper?   Note  its  adaptation  to  the  storage  of  blood. 


EXERCISE  6 

COMPARATIVE  STUDY  OF  THE  BITING  AND  SUCKING  LICE 

Use  for  this  exercise  slide  mounts  in  balsam  of  Hamatopinus 
piliferus,  the  sucking  louse  of  the  dog,  and  either  Trichodectes 
lotus,  the  biting  louse  of  the  dog,  or  Trichodectes  scalaris,  the 
biting  louse  of  cattle. 

The  biting  lice  belong  to  the  order  Mallophaga,  while  the 
sucking  lice  belong  to  the  Order  Hemiptera,  Family  Pediculidae. 
These  two  groups  of  parasites  are  not  always  easily  distinguish- 
able without  the  use  of  a  compound  microscope.  The  bodies  of 
both  are  flattened  dorso-ventrally,  and  in  both  wings  are  absent. 

With  a  mounted  specimen  of  each  in  hand,  examine  them 
under  a  compound  microscope  (low  power)  and  determine  the 
following  characters,  drawing  each  specimen.  Your  drawings 
should  be  large  enough  to  cover  at  least  half  a  page  of  ordinary 
notebook  size. 


ORDER   MALLOPHAGA  15 

a.  Compare  the  head,  thorax  and  abdomen,  noting  the  rela- 
tively small  thorax  as  compared  with  that  of  the  housefly,  for 
example. 

b.  The  appendages  differ  how?     Note  the  claws  of  each 
species  and  explain  the  difference  on  the  basis  of  the  relative 
activity  of  the  insects.    The  sucking  lice  generally  and  many 
species  of  the  biting  lice  have  heavy  clasping  structures. 

c.  Determine  the  position  of  antenna  and  eyes,  if  present. 

d.  Study  the  mouthparts  of  each  species.    Note  the  rather 
sharp  mandibles  of  the  biting  louse.    Where  are  the  mouthparts 
located?    Observe  the  proboscis  of  a  sucking  louse  in  which  that 
organ  is  protruded.    What  is  the  position  of  that  organ  when 
the  insect  is  not  actively  feeding? 

e.  Search  for  traces  of  blood  in  the  stomachs  of  both  species. 


EXERCISE  6a 

ORDER  MALLOPHAGA  (BIRD  LICE) 

Anatomical  Study. 

Using  a  slide  mount  of  the  common  hen  louse  (Menopon 
pallidum)  determine  the  following  parts,  making  a  large  drawing 
of  the  specimen: 

a.  Head,  thorax,  abdomen. 

b.  Antenna, — are   they   clavate    (club-shaped)    or    capitate 
(ending  in  a  distinct  knob)?    Determine  number  of  segments. 

c.  Mandibles. 

d.  Eyes. 

e.  Temples,  posterior  lateral  portions  of  the  head. 

f .  Ocular  emarginations,  a  bending  in  of  the  lateral  margins  of 
the  head  just  in  front  of  the  eyes. 

g.  Sternal  markings, — blackish  markings,  bars  or  spots,  on 
the  ventral  aspect  of  the  thorax.    (May  not  be  visible.) 

h.  Tarsal  claws,  whether  paired  or  single,  whether  strongly 
adapted  for  clasping  hairs  and  feathers  or  not. 


1 6  MEDICAL  ENTOMOLOGY 

EXERCISE  6b 

ORDER  MALLOPHAGA  (BIRD  LICE) 

Systematic  Study. 

As  representatives  of  the  families  of  the  Order  Mallophaga 
the  following  are  available: 

A.  Suborder  Ischnocera. 

a.  Family  Trichodectidae. 

Genus  Trichodectes,  examples,  T.  latus  and  T. 

b.  Family  Philopteridae. 

Genus  Lipeurus,  example,  L.  polytrapezius,  the  long  turkey 
louse. 

Genus  Goniodes,  examples,  G.  stylifer  of  the  turkey  and 
G.  dissimilis  of  the  hen. 

B.  Suborder,  Amblycera. 

a.  Family  Gyropidae. 

Genus  Gyropus,  examples,  G.  sp.  from  ground-squirrel. 

b.  Family  Liotheidae. 

Genus  Menopon,  examples  M.  pallidgm.  the  common  hen 
louse  and  M.  biseriatum,  also  from  hens. 

Genus  Trinoton,  example,  T.  luridum,  the  duck  louse. 
As  representatives  of  the  Trichodectidae  and  Liotheidae  have 
previously  been  drawn,  draw  one  example  each  of  the  two  re- 
maining families,  Philopteridae  and  Gyropidae. 

EXERCISE  7a 

ORDER  HEMIPTERA,  SUBORDER  PARASITA,  FAMILY  PEDICULID^ 

THE  SUCKING  LICE  OF  MAMMALS 

Anatomical  Study. 

The  suctorial  lice  are  wingless,  as  are  the  biting  lice,  and  the 
two  may  be  confused,  if  attention  is  not  paid  to  the  structure  of 


ORDER   HEMIPTERA  17 

the  mouthparts.  Furthermore,  the  heads  of  members  of  the 
former  order  are  usually  much  more  elongate  in  proportion  to 
the  size  of  the  body  than  is  the  case  in  the  Mallophaga.  The 
claws  of  the  Parasita  are  also  strongly  developed  for  clasping  and 
clinging  to  hairs. 

Examine  a  mounted  specimen,  using  the  hog  louse  (Hcema^ 
iopinus  suis}  as  an  example  of  the  order,  and  note  the  distinctions 
above  mentioned. 

The  proboscis  of  the  sucking  louse  is  fleshy  and  un jointed,  sur- 
rounded at  its  base  by  a  circlet  of  barbs,  and  is  in  the  form  of  an 
extensile  tube  provided  with  lancets.  The  legs  are  short  and 
stout,  and  the  tarsus  is  provided  with  a  strong  opposable  claw. 

Draw  the  specimen,  showing  the  general  structure. 


EXERCISE  7b 

ORDER  HEMIPTERA,  SUBORDER  PARASITA,  FAMILY  PEDICULIDJE 

Systematic  Study. 

The  Suborder  Parasita  includes  two  families,  only  one  of 
which  needs  to  be  considered  here.   The  other  family  is  Oriental, 
and  is  found  solely  on  bats. 
Family  Pediculidae. 

Genus  Pediculus,  examples,  P.  capitis,  the  head  louse  of  man, 
and  P.  vestimenti,  the  body  louse  of  man. 

Genus  Phthirius,  example,  P.  inxuinalis.  the  crab  louse  of  man. 

Genus  Haematopinus,  examples,  H.  piliferus,  the  sucking 
louse  of  the  dog,  H.  suis,  of  the  hog,  H.  macrocephalus,  the 
horse  louse,  and  H.  spinulosus,  the  sucking  louse  of  the  rat. 

Examples  of  the  Genus  Haematopinus  having  been  drawn 
previously,  make  large  drawings  of  one  example  each  of  the 
genera  Pediculus  and  Phthirius. 


1 8  MEDICAL  ENTOMOLOGY 

EXERCISE  8a 

THE  BEDBUG 

ORDER  HEMIPTERA,    FAMILY  ACANTHIID,E 

A.  Characteristics  of  Hemiptera. 

The  Hemiptera  usually  possess  two  pairs  of  wings  (except, 
e.  g.  the  Acanthiidae  and  Pediculidae),  the  front  wings  (wing- 
covers)  in  the  Hemiptera-Heteroptera  are  partly  leathery,  and 
membranous  at  the  apices.  The  mouthparts,  as  already  studied, 
are  piercing,  suctorial,  typically  three- jointed,  closely  ensheath- 
ing  three  or  four  setae. 

B.  Characteristics  of  Acanthiida. 

A  group  of  wingless  insects  with  extremely  flattened  bodies, 
giving  off  a  pungent  odor.  The  color  is  reddish  brown.  An- 
tennae are  four-jointed. 

a.  Examine  a  mounted  specimen  of  Cimex  kctulariys,  the 
common  bedbug,  for  the  above  indicated  characteristics.  Draw 
the  specimen. 

EXERCISE  8b 

THE  CONE-NOSES 

ORDER  HEMIPTERA,   FAMILY  REDUVIIDJE 

A.  Characteristics  of  Redumida. 

This  is  a  group  of  predaceous  insects,  fore  wings  partly 
leathery,  distal  portion  membranous.  The  head  is  long  and 
joined  to  the  body  by  a  slender  neck.  The  tip  of  the  head  is  cone- 
shaped,  with  a  three-jointed  heavy  rostrum  which  curves  under- 
neath the  body.  The  antennae  are  long  and  slender.  The  legs 
are  prominent  and  give  the  insect  a  sprawled  out  appearance. 


MOSQUITOES  19 

B.  Examine  the  following  common  species,  noting  color  and 
color  markings  in  particular.  Draw  side  view  of  (a),  and  dorsal 
view  of  (d). 

a.  Melanolestes  picipes — the  China  bedbug. 

b.  Melanolestes  abdominalis — also  called  the  China  bedbug. 

c.  Reduvius  personatus — the  Eastern  kissing  bug. 

d.  Rasahus  biguttatus — the  two  spotted  corsair. 

e.  Conorhinus  sanguisuga — the  blood-sucking  cone-nose. 


EXERCISE  9 

MOSQUITOES 

ORDER   DIPTERA,   FAMILY  CULICIDuE 

With  specimens  of  mosquitoes  before  you,  study  them  with 
a  hand  lens  for  (A)  and  with  a  compound  microscope  for  (B). 

A.  a.  One  pair  of  membranous  wings. 

b.  The  legs  are  long  and  slender.    Note  the  following  parts, 
femur,  tibia,  and  tarsus,  the  latter  segmented. 

c.  On  the  head  are  located  the  prominent  eyes,  the  antenna, 
and  proboscis,  with  its  pair  of  palpi.    Note  the  relative  length 
of  the  palpi  with  reference  to  the  proboscis. 

B.  a.  Examine  the  wings  and  body  for  scales,  a  feature  char- 
acteristic of  the  mosquitoes. 

b.  Examine  the  tarsal  claws,  noting  whether  they  are  double 
or  single  toothed  or  not  toothed. 

Draw  a  number  of  head  scales,  and  the  tarsal  claws. 

C.  Sexual  differences. 

a.  Examine  the  antenna  of  a  male  and  of  a  female  specimen, 
and  note  the  plumose  condition  in  the  former  sex. 

D.  Characteristics  of  the  Anopheles,  or  malaria  mosquito,  as 
compared  with  the  Culex,  or  rain-barrel  mosquito. 

a.  Is  there  any  difference  in  size? 


20  MEDICAL  ENTOMOLOGY 

b.  Compare  the  palpi,  note  the  extreme  length  in  Anopheles, 
nearly  as  long  as  the  proboscis,  while  in  Culex  they  are  less  than 
half  as  long. 

c.  Examine  the  wings  for  markings,  spots,  etc.     Note  that 
Anopheles  has  spotted  wings,  which  is  the  case  in  only  a  very 
few  species  of  Culex. 

Draw  the  head  and  its  appendages  in  Anopheles. 

E.  Compare  the  larva  (wrigglers)  of  Anopheles  and  Culex. 

a.  Note  the  long  prominent  breathing  tube  or  anal  siphon  of 
Culex,  short  in  Anopheles. 

b.  Note  the  arrangement  of  the  tufts  of  hairs  on  the  thorax 
and  abdomen.    The  anal  tuft  is  especially  prominent. 

c.  Count  the  number  of  body  segments  comprising  the  ab- 
dominal region. 

d.  Examine  the  palmate  hairs  situated  dorsally  on  abdominal 
segments. 

e.  On  the  head  note  the  presence  of  eyes,  antenna  and  mouth 
brushes. 

Draw  the  larvae  of  both  species,  and  label  parts. 

F.  Compare  the  pupa  (tumblers)  of  Anopheles  and  Culex. 

a.  Examine  the  prominent  breathing  trumpets  (air  siphons) 
situated  laterally  and  dorsally  on  the  thorax.     Compare  the 
breathing  trumpets  as  to  shape  and  position. 

Draw  an  Anopheles  tumbler. 

G.  Examine  a  slide  of  mosquito  eggs. 
Draw  several  specimens. 

H.  a.  Examine  specimens  of  the  yellow  fever  mosquito  (Steg- 
omyia  calopus}  and  note  the  prominent  silvery  markings.  How 
are  these  markings  distributed? 

b.  What  is  the  length  of  the  palpi  as  compared  with  the  pro- 
boscis?   Note  other  characteristics. 

Draw  a  dorsal  view  of  the  insect. 


THE   HORSEFLIES  21 

EXERCISE  lOa 

BUFFALO  GNATS 
ORDER  DIPTERA,  FAMILY  SIMULIID^ 

A.  The  buffalo  gnats  or  black  flies  are  widely  distributed;  all 
species  are  small,  the  largest  less  than  %  inch  in  length.    Any 
of  the  common  species  of  Simulium  will  serve  for  this  study. 
Specimens  mounted  in  balsam  are  needed  for  microscopic  study. 

a.  Note  the  humped  condition  of  the  thorax,  giving  the  insect 
a  buffalo-like  appearance. 

b.  The  antenna  are  short  and  stalky,  but  Nematoceron  in 
character. 

c.  Notice  the  characteristic  venation  of  the  rather  large  broad 
wings.    The  first  three  longitudinal  wing  veins  are  very  much 
stronger  than  the  rest. 

d.  Examine  the  mouthparts  carefully.    To  what  subtype  to 
the  mouthparts  belong? 

Draw  the  specimen  in  outline. 

B.  If  larvae  of  the  buffalo  gnats  are  available  examine  speci- 
mens carefully  and  determine  their  adaptation  to  an  aquatic 
habitat. 

Draw  a  specimen. 

EXERCISE  lOb 

THE  HORSEFLIES 
ORDER  DIPTERA,  FAMILY  TABANIDJS 

Anatomical  Study. 

With  a  specimen  of  Tabanus  stygius,  Tabanus  punctifer  or 
other  allied  species  before  you,  note  the  following  characteristics, 
and  make  drawings  of  the  parts. 


22  MEDICAL  ENTOMOLOGY 

a.  Antenna, — three-jointed,  terminal  segment  annulated,  and 
not  possessing  the  arista  of  the  housefly  and  its  allies. 

b.  Last  tarsal  segment,  note  the  claws,  pulvilli  and  empodium 
between. 

c.  Head,  note  the  large  compound  eyes,  separated  in  the  female 
and  contiguous  in  the  male;  note  the  sexual  difference  in  size  of 
mouthparts. 

EXERCISE  lOc 

THE  HORSEFLIES 

Systematic  Study. 

Family  Tabanidae,  antennae  porrect,  without  arista,  medium 
sized  to  large  flies. 

1.  Genus   Tabanus, — hind   tibiae  without  spurs,  third  seg- 
ment of  the  antennae  with  a  well  developed  basal  process,  ex- 
amples, T.  stygius,  the  black  and  white  horsefly;  T.  punctifer; 
T.  atratus,  the  black  horsefly;  T.  costalis,  the  greenhead;  and 
T.  lineola,  the  lined  horsefly. 

2.  Genus  Chrysops, — (Earflies  or  Deerflies) — hind  tibiae  with 
spurs  at  tip,  third  segment  of  the  antennae  composed  of  five 
annuli;  second  segment  of  the  antennae  but  little  shorter  than 
the  first;  wings  with  a  dark  picture;  examples,  C.  niger  and  C. 
bruneus. 

Draw  one  example  each  of  the  two  genera  mentioned  above. 

EXERCISE  11 

THE  HOUSEFLY   (MUSCA  DOMESTICA)    AND  THE  STABLEFLY 
(STOMOXYS  CALCITRANS) 

ORDER  DIPTERA,  FAMILY  MUSCID® 

A  Comparative  Study. 

It  will  be  remembered  that  while  these  two  species  of  flies 


THE   HORSEFLIES  23 

belong  to  the  same  family  of  insects  (Muscidae),  they  differ 
nevertheless  greatly  in  their  powers  of  disease  transmission,  the 
former  relating  to  indirect  infection  and  the  latter  to  direct 
infection. 

With  a  specimen  of  each  species  of  fly  before  you,  note  the 
distinguishing  features,  indicating  the  same  by  means  of  separate 
drawings  of  the  parts,  and  by  description  in  your  notebooks. 

a.  Mouthparts;  note  the  characteristic  position  of  these  organs 
at  rest. 

b.  Wing  venation;  draw  the  right  wing  of  each  species,  care- 
fully drawing  in  the  wing  veins.    Note  the  differences  in  venation 
by  crossing  (x)  the  parts  that  vary,  both  cells  and  veins. 

c.  Coloration;  indicate  any  differences  in  color,  or  color  mark- 
ings, that  you  may  observe. 

d.  Note  any  other  differences  in  position  of  the  wings,  relative 
length  of  body,  size,  etc. 

e.  Sexual  differences;  ask  your  instructor  for  specimens  of  the 
housefly  representing  the  two  sexes.    Note  that  in  the  female 
the  compound  eyes  are  widely  separated,  whereas  in  the  male 
the  dorsal  borders  come  close  together.     In  the  female  the 
terminal  segments  are  protrusible,  which  should  be  demonstrated 
by  pinching  the  abdomen  with  the  finger  or  forceps.    The  pro- 
trusible segments  make  up  the  ovipositor. 

f.  Study  a  life  history  preparation  of  both  the  housefly  and 
the  stablefly,  showing  the  egg,  larva  and  pupa.    Compare  es- 
pecially the  posterior  spiracles  of  the  larva,  and  pupa  with  refer- 
ences to  position,  form  and  size.    (Draw.) 


24  MEDICAL  ENTOMOLOGY 

EXERCISE  12 

THE  STABLEFLY  (STOMOXYS  CALCITRANS)  AND  THE  HORNFLY 
OR  TEXAS  FLY  (HEMATOBIA  SERRATA) 

ORDER  DIPTERA,   FAMILY  MUSCID2E 

A  Comparative  Study. 

With  specimens  of  each  species  of  fly  before  you,  note  the 
distinguishing  characteristics,  indicating  the  same  by  means  of 
separate  drawings  of  the  parts  and  by  description  in  your  note- 
book. 

These  two  species  of  flies  belong  to  the  blood-sucking  branch 
of  the  Family  Muscidae,  to  which  also  belongs  the  genus  Glos- 
sina  (Tsetse  flies). 

a.  Mouthparts.    The  palpi  of  Stomoxys  are  relatively  short, 
while  those  of  Haematobia  are  long  and  flattened.     The  pro- 
boscis of  the  latter  is  also  relatively  more  plump  and  is  not  so 
well  thrown  forward,  when  at  rest,  as  in  the  Stomoxys,  due  in 
the  latter  to  a  well  developed  joint  at  its  base. 

b.  Wings.    Note  the  close  similarity  in  wing  venation.    The 
wings  of  the  stablefly  are  thrown  wide  apart  when  at  rest.        f 

c.  Size.    With  at  least  half  a  dozen  specimens  of  each  species 
before  you  note  the  relative  size  of  the  individuals.    Measure 
the  length  of  these  specimens  in  terms  of  millimeters. 

d.  Make  a  large  drawing  of  the  head  of  the  hornfly,  side  view, 
to  show  the  following  parts,  compound  eye,  antenna,  and  pro- 
boscis with  palpi. 

e.  Draw  the  egg  of  the  hornfly;  note  the  brownish  color.    En- 
large sufficiently  to  indicate  general  characteristics. 

f.  Note  differences  in  the  sexes  as  indicated  by  the  segments 
of  the  abdomen. 


FLESH-FLIES  25 

EXERCISE  13 

FLESH-FLIES 

*-        •      w 

ORDER  DIPTERA,   FAMILY  SARCOPHAGIDJE . 

Family  Sarcophagidae — thorax  and  abdomen  provided  with 
stiff  bristles.    (Do  not  confuse  with  the  Tachinidae.) 

A.  The  Texas  screw  worm  fly,  Chrysomyia  (Lucilia)  macel- 
laria. 

a.  Coloration;  general  color  of  the  body  is  metallic  green;  the 
thorax  bears  three  longitudinal  black  dorsal  stripes.    The  head 
is  distinctly  reddish  brown  in  color. 

b.  Size;  the  size  of  all  species  of  flesh  flies  may  vary  consider- 
ably within  each  group,  due  largely  to  lack  of  food  during  the 
larval  period.    (See  Herms,  "An  Ecological  and  Experimental 
Study  of  Sarcophagidae,"  1906.)     However  the  screw  worm  fly 
is  a  medium-sized  fly,  never  attaining  the  size  of  the  larger 
species  of  flies,  such  as  the  blowfly,  Calliphora  wmitoria,  for 
example. 

c.  Mouthparts;  compare  with  mouthparts  of  housefly. 

d.  Wing  -venation;  compare  with  venation  of  housefly. 

e.  Note  the  scissors-like  folding  of  the  wings.      Draw  the 
specimen,  indicating  the  striping  and  the  characteristic  folding 
of  the  wings,  in  particular. 

B.  Examine  and  draw  a  specimen  of  the  bluebottle  fly,  Cal- 
liphora wmitoria.    What  are  its  characteristics? 

C.  Examine  and  draw  a  specimen  of  the  greenbottle  fly, 
Lucilia  c&sar.    How  does  this  species  differ  from  Chrysomyia? 

D.  Study  and  draw  mounted  specimens  of  flesh  fly  larvae, 
noting  the  oral  hooks,  or  mandibles,  shape,  color  and  posterior 
spiracles. 


26  MEDICAL  ENTOMOLOGY 

EXERCISE  14 

THE  Box  AND  WARBLE  FLIES 

ORDER  DIPTERA,    FAMILY  CESTRnXdE 

A.  With  two  specimens  of  (Estridae  before  you,  one  Gastro- 
philus  equi,  the  horse  hot,  and  one  Hypoderma  lineata,  the 
ox  warble  fly,  study  the  following  characters,  noting  that  the 
examples  are  rather  thickset  and  covered  with  hair,  and  that 
the  mouthparts  are  vestigial,  the  eyes  small  and  bare,  the 
squamae  large. 

a.  Antenna  are  small,  three-jointed  and  decumbent,  as  in  the 
Muscidae.    In  the  horse  bot  the  arista  is  bare,  while  in  the 
warble  fly  it  is  plumose. 

b.  Tarsi  of  front  legs,  broad,  flattened  and  hairy  in  Hypo- 
derma,  while  they  are  slender  and  less  hairy  in  Gastrophilus. 

c.  Wing  venation;  note  the  difference  between  the  genera. 

d.  Sexual  characters;  notice  the  difference  between  the  sexes 
in  the  terminal  abdominal  segments. 

Draw  the  characteristic  details. 

B.  Larval  Characters. 

a.  Segmentation;  count  the  segments,  paying  especial  attention 
to  the  terminal  ones. 

b.  Booklets;  in  the  horse  bot  note  the  presence  of  a  pah-  of 
outer  booklets  used  for  attachment  to  the  walls  of  the  stomach. 
Note  also  a  pair  of  inner  straight  points  (not  hooked).   Are  these 
anterior  or  posterior? 

c.  Tubercles;  in  the  warble  notice  the  dorsal  spindle-shaped 
tubercles  on  the  median  segments  and  then*  arrangement. 

d.  Examine  a  specimen  of  the  head  maggot  of  sheep  ((Estrus 
ovis). 

Draw  a  specimen  of  each. 


THE  FLEAS  27 

EXERCISE  15a 

THE  FLEAS 

ORDER  SIPHONAPTERA 

Anatomical  Study. 

In  order  to  find  the  following  characters  two  species  of  fleas 
should  be  used,  namely,  the  human  flea  (Pulexirritans),  and  the 
dog  flea  (Ctenocephalus  canis).  Note  the  entire  absence  of 
wings  and  the  characteristic  laterally  compressed  condition  of 
the  body  ,with  legs  strongly  developed  for  springing. 

a.  Legs;  observe  the  greatly  elongated  coxa,  and  other  seg- 
ments. 

b.  Mouthparts;  composed  of  sharp  piercing  structures;  a  de- 
tailed study  of  which  may  be  omitted  here. 

c.  Antenna;  short,  three-segmented,  usually  sunken  in  a  pit. 
The  terminal  segment  is  swollen  and  annulated. 

d.  Combs;  rows  of  spines  on  the  head  (oral),  and  thorax  (pro- 
notal),  forming  combs  (ctenidia)  are  used  to  separate  the  fleas  of 
the  family  Pulicidae  into  the  combed  and  non-combed  species. 
The  number  of  spines  in  each  comb  is  also  useful  for  classifica- 
tion.   In  the  dog  flea  notice  the  two  rows  of  combs  and  count  the 
number  of  spines  in  each. 

e.  Eyes,  which  may  be  present  or  absent,  are  of  a  simple  type. 

f.  Examine  and  draw  a  specimen  of  flea  larva. 

g.  Examine  and  draw  specimens  of  flea  eggs. 
Draw  one  example  of  each  species  of  flea. 


28  MEDICAL  ENTOMOLOGY 

EXERCISE  16b 

THE  FLEAS 

ORDER   SIPHONAPTERA 

Systematic  Study. 

Order  Siphonaptera — wingless  insects,  laterally  compressed, 
body  highly  chitinized,  provided  with  many  regularly  arranged 
spine-like  hairs. 

A.  Family  Sarcopsyllidae,  "Small  fleas  with  disproportion- 
ately large  heads;  female  a  stationary  parasite  with  worm-like 
or  spherical  abdomen,  burrowing  into  the  flesh  of  the  host;  labial 
palpi  one-segmented;  no  *  combs'  of  spines  on  head,  thorax  or 
abdomen"  (Kellogg). 

a.  Examples,  Sarcopsylla  penetrans,  the  jigger-flea  or  chigoe 
of  mammals,  including  man. 

b.  Xestopsylla  gallina,  the  hen  flea. 

B.  Family  Pulicidae,  "larger  fleas  with  proportionately  small 
head;  adults  active  temporary  parasites,  with  abdomen  always 
compressed;  labial  palpi  3  to  5  segmented;  head,  thorax  or 
abdomen  often  with  'combs'  of  spines"  (Kellogg). 

a.  Examples,  Pulex  irritans,  the  human  flea,  non-combed. 

b.  Ctenocephalus  canis,  the  dog  and  cat  flea,  two  sets  of 
combs,  one  oral  and  one  thoracic. 

c.  Ceratophyllus  fasciatus,  the  rat  flea,  thoracic  comb  present, 
but  oral  comb  absent. 

d.  Ceralophyllus   acutus,    the   squirrel   flea,    thoracic   comb 
present,  consisting  of  nine  spines  on  one  side. 

Draw  the  hen  flea  and  either  the  rat  flea  or  the  squirrel  flea. 


THE  TICKS  29 

EXERCISE  16 

LOUSE  FLIES 

ORDER  DIPTERA,  FAMILY  HIPPOBOSCIDdE 

A.  The  louse  flies  are  extremely  chitinous,  dorso-ventrally 
flattened   insects,   with   suctorial  mouthparts.      Most  of  the 
species  are  winged,  and  are  often  also  called  forest  flies;  the 
wingless  species  are  called  "ticks,"  but  should  not  be  confused 
with  the  true  ticks  (Ixodidae). 

B.  Study  a  specimen  of  the  sheep  "tick,"  Melophagus  ovi- 
nus,  noting  the  following  characteristics: 

a.  Louse-like  form  and  reddish  color. 

b.  The  head  is  extremely  small  and  the  proboscis  is  prominent. 

c.  The  species  is  wingless. 
Draw  the  specimen. 

C.  Examine  a  puparium  of  Melophagus  ovinus. 

D.  If  available,  compare  a  deer  "tick,"  Lipoptena  depressa 
with  the  above. 

E.  The  forest  fly,  Hippobosca  equina,  is  a  winged  species. 

a.  In  what  respects  does  this  species  differ  fromMelophagus 
ovinus?    In  what  respects  do  the  two  agree? 
Draw  the  specimen. 

-:.>VU^W> 

EXERCISE  17a 


THE  TICKS 

ORDER  ARACHNIDA,   FAMILY  IXODIDAE 

Anatomical  Study. 

Ticks  belong  to  the  same  group  as  do  the  spiders,  and  therefore 
have  four  pairs  of  legs  in  the  adult  stage.    With  a  specimen  of  the 


30  MEDICAL  ENTOMOLOGY 

wood  tick  (Dermacentor  variabilis)  or  the  Texas  fever  tick 
(Mar gar  opus  annulatus),  before  you,  study  and  draw  the  follow- 
ing characters,  making  one  drawing  of  the  whole  animal  and 
separate  drawings  necessary  to  show  the  details. 

a.  Rostrum,  consisting  of  the  head  and  mouthparts. 

b.  Labium  or  hypostome,  a  continuation  forward  of  the  head 
(snout-like)  possessing  longitudinal  rows  of  teeth. 

c.  Mandibles  or  cheliceres,  one  pair,  terminating  in  well  de- 
fined teeth.    The  cheliceres  work,  each  in  a  separate  sheath. 

d.  Palpi  or  pedipalpi,  segmented  structures  varying  consider- 
ably in  relative  length  in  the  various  genera. 

e.  The  eight  legs  are  composed  of  the  following  parts:  coxa, 
trochanter,  femur,  tibia,  protarsus,  tarsus,  ungues   (claws)   and 
pulvillus  (absent  in  Argasinae). 

f .  Scutum  or  shield,  a  chitinous  plate  covering  a  portion  of  the 
dorsal  part  of  the  body  back  of  the  head.    This  shield  is  often 
ornamented  with  spots,  furrows  and  perforations. 

g.  Eyes,  present  in  Dermacentor  and  a  few  other  genera,  but 
absent  in  a  number  of  other  genera,  including  Margaropus. 

h.  Anus,  ventrally  located,  removed  from  the  posterior  border 
and  guarded  by  anal  plates. 

i.  Anal  groove,  a  furrow  either  posterior  or  anterior  to  the 
anus,  depending  on  the  genus,  and  useful  in  classification. 

j.  Spiracles  with  guard  plates, — situated  laterally  and  ven- 
trally, in  some  species  in  front  of  the  fourth  coxae,  or  in  some 
behind  the  fourth  coxae. 

fc.  Marginal  festoons;  the  marginal  border  of  the  abdomen  is 
often  crenellated. 

1.  Sexual  differences;  the  shield  or  scutum  of  the  male  covers 
the  greater  part  of  the  dorsum,  while  in  the  female  it  extends 
over  only  a  small  portion  posterior  to  the  head.  The  male  is 
usually  considerably  the  smaller  and  more  slender,  and  is  louse- 
like  in  appearance.  Though  this  is  true  for  the  Ixodinae,  to 
which  group  the  specimens  studied  belong,  in  the  Argasinae  the 
sexes  are  more  difficult  to  distinguish. 


OTHER  TICKS  31 

EXERCISE  17b 

THE  TICKS 


ORDER  ARACHNIDA,   FAMILY  IXODIRffi 

Systematic  Study. 
Family  Ixodidae. 

A.  Subfamily    Ixodinae,   scutum    present,   pulvilli    present, 
mouthparts  projecting  in  front. 

a.  Examples:  Mar  gar  opus  annulatus,  Texas  fever  tick  or  blue 
tick,  scutum  uniformly  chestnut  brown  in  color,  labium  or 
hypostome  with  eight  rows  of  teeth.    Front  pair  of  legs  emerging 
from  the  shoulders.    What  is  the  form  of  the  guard  plates  of  the 
spiracles? 

b.  Dermacentor  variabilis,  American  dog  tick,  scutum  spotted 
with  silver.     Front  pair  of  legs  emerging  close  to  capitulum. 
What  is  the  form  of  the  guard  plates  of  the  spiracles? 

B.  Subfamily    Argasinae,    scutum    absent,    pulvilli    absent, 
mouthparts  hidden  under  body. 

a.  Examples:  Argas  miniatus,  American  poultry  tick,  body 
flat  with  thin  edges,  body  oval,  with  rectangular  marginal  fes- 
toons. 

b.  Ornithodorus  megnini,  the  spinous  ear  tick,  body  lyre- 
shaped  and  covered  with  spines. 

Draw  from  specimens,  using  hand  lens  or  binocular  micro- 
scope the  three  species  not  previously  drawn. 


EXERCISE  18a 

OTHER  TICKS 

As  far  as  it  is  possible  to  secure  material  examine  specimens  of 
the  following  species  of  ticks,  taking  notes  and  making  drawings 


32  MEDICAL  ENTOMOLOGY 

of  the  same  to  fix  the  general  characteristics  of  each  in  your 
mind. 

A.  Ixodinae. 

a.  Amblyomma  americanum  is  the  Lone  Star  tick.     Notice 
the  bright  silvery  spot  at  the  posterior  end  of  the  scutum. 

b.  Dermacentor  venustus  is   the   Rocky   Mountain   spotted 
fever  tick.    Notice  the  large  size  of  the  scutum,  which  has  a 
dark  lyre-shaped  figure  upon  it  on  a  silvery  background. 

c.  Rhipicephalus  sanguineus  is  the  brown  dog  tick. 

d.  Ixodes  scapularis  is  the  black  legged  tick  or  American 
castor  bean  tick;  the  scutum  is  chestnut  colored  as  in  the  Texas 
fever  tick,  but  the  body  has  the  shape  of  a  castor  bean,  the  legs 
are  black,  and  emerge  from  the  body  quite  close  to  the  mouth- 
parts. 

e.  Rhipicephalus  appendiculatus  is  one  of  the  ticks  respon- 
sible for  the  transmission  of  African  coast  fever  of  cattle. 

B.  Argasinae. 

a.  Ornithodorus  moubata  is  responsible  for  the  transmission 
of  African  relapsing  fever  of  man. 

b.  Argas  persicus  is  the  Persian  poultry  tick,  to  which  Argas 
miniatus  is  very  closely  related.    These  ticks  are  responsible  for 
the  transmission  of  Fowl  Spirochaetosis. 


EXERCISE  18b 

LIFE  HISTORY  STUDY  OF  THE  TICKS 

A.  Examine  a  prepared  slide  of  tick  eggs. 

B.  If  available,  examine  an  ovulating  female  tick.     Notice 
that  the  mass  of  eggs  lies  anterior  to  the  body,  with  the  head 
buried  in  it.    Why? 

C.  Examine  mounted  specimens  of  ticks  that  have  recently 
emerged  from  eggs,  noting  particularly  the  number  of  legs.   ; 


THE  MITES  33 

D.  Compare  specimens  of  young  female  ticks  with  specimens 
that  are  fully  engorged. 

E.  Examine  again  a  series  of  males  and  females  of  several 
species,  to  determine  sexual  differences. 


EXERCISE  19a 

I 

THE  MITES 

CLASS  ARACHNIDA,  ORDER  ACARINA,  FAMILY  GAMASIH£ 

A.  General  characteristics  of  mites;  usually  quite  small,  just 
about  visible  to  the  naked  eye,  some  larger.    The  body  portions 
are  more  or  less  closely  united.    The  mouthparts  are  piercing 
and  sucking  structures.    The  four  pairs  of  legs  are  generally 
well  developed,  terminating  in  suckers.    The  sexes  are  separate. 
The  young  are  hexapod. 

B.  Characteristics  of  Gamasidce;  the  legs  are  six-segmented  and 
terminate  in  a  pair  of  ungues  and  a  sucker-like  disc.    The 
stigmata  or  breathing  pores  are  located  between  the  third  and 
fourth  pairs  of  legs. 

C.  The  poultry  mite,  Dermannyssus  gallina.     Study  speci- 
mens mounted  in  balsam. 

a.  Measure  size  of  the  specimens.    How  do  the  males  and  fe- 
males differ  in  this  respect? 

b.  Note  the  position  of  the  legs  with  respect  to  the  body 
divisions. 

c.  Count  the  segments  of  a  leg  and  note  the  terminal  struc- 
tures. 

d.  Locate  the  stigmata. 

Draw  the  specimen,  labelling  the  parts. 


34  MEDICAL  ENTOMOLOGY 

EXERCISE  19b 

THE  MITES 

CLASS   ARACHNIDA,    ORDER  ACARINA,   FAMILY   SARCOPTID2E 

A.  Characteristics  of  Sarcoptida.    The  legs  are  six-segmented, 
short  and  thick,  and  terminate  in  a  sucker  or  a  slender  bristle 
ending  in  a  disc-like  sucker. 

B.  Sat -copies  scabei  var.  suis.    This  variety  of  itch  mite  in- 
habits the  skin  of  the  domestic  pig,  tunneling  its  way  through 
the  epidermis,  causing  a  scaly  appearance.    This  variety  may 
also  attack  man. 

a.  Note  the  minute  size  of  this  species.    How  does  it  compare 
with  the  poultry  mite  in  this  respect? 

b.  How  does  it  compare  in  color  with  the  poultry  mite? 

c.  What  is  the  form  of  the  body  and  position  of  legs? 

d.  Note  the  transverse  rows  of  bristles  on  the  dorsal  surface  of 
the  mite. 

e.  Study  the  .terminal  structures  of  the  leg,  noting  especially 
the  spines  and  sucker  (ambulacrum). 

Draw  the  specimen. 

EXERCISE  20 

OTHER  MITES 

CLASS  ARACHNIDA,  ORDER  ACARINA,  FAMILY  SARCOPTHXE  (cont.) 

A.  Psoroptes  communis  var.  ovis  is  the  scab  mite  of  sheep, 
producing  scabies.  Comparing  this  Psoroptic  mite  with  the 
Sarcoptic  mites,  notice  the  following  characteristics: 

a.  The  body  is  elongate  oval. 

b.  All  four  pairs  of  legs  appear  beyond  the  margin  of  the  body. 


THE  INSECT    STING  35 

c.  The  third  pair  of  legs  is  devoid  of  ambulatory  suckers,  and  in 
their  place  note  a  long  pair  of  bristles  for  each  leg. 
Draw  a  female  specimen. 

B.  Psoroptes  communis  var.  boms  is  the  mange  mite  of  the  ox. 
a.  Can  you  find  any  perceptible   difference  between  this 

species  and  the  one  above? 

C.  Psoroptes  communis  var.  equi  is  the  mite  which  causes 
humid  mange  of  the  horse. 

a.  The  rostrum  is  characteristically  long,  twice  as  long  as 
broad,  otherwise  the  species  differs  but  imperceptibly  from  the 
species  above. 

D.  Sar copies  scabiei  var.  canis  is  one  of  the  mange  mites  of 
the  dog. 

a.  Notice  similarity  to  the  variety  inhabiting  swine. 

E.  Sarcoptes  mutans  is  the  parasite  which  causes  scaly  leg 
in  poultry. 

Examine  a  bit  of  mounted  scrapings  from  the  leg  of  a  hen 
affected  with  scaly  leg.  The  circular  mites  (typically  Sarcoptic) 
are  easily  visible. 

Draw  the  specimen. 


EXERCISE  21a 

THE  INSECT  STING 

The  insect  sting,  as  found  in  the  Hymenoptera  (bees,  wasps 
and  ants)  is  a  modified  ovipositor,  the  function  having  been 
changed  from  that  of  an  egg  apparatus  to  that  of  a  defensive 
weapon.  In  many  insects  the  sting  still  serves  both  purposes. 

A  fresh  worker  bee  should  be  used  for  study;  these  can  usually 
be  procured  at  a  nearby  apiary,  or  bees  may  be  killed  hi  the 
field  just  before  using. 

With  a  needle  remove  the  last  evident  scale-like  segment  of 
the  abdomen,  which  will  bring  with  it  the  sting,  the  venom  sac 


36  MEDICAL  ENTOMOLOGY 

and  much  of  the  alimentary  canal.  The  sting  can  be  recognized 
at  once  as  a  fine  needle-like  structure,  and  the  venom  sac  as  a 
very  small  semi-transparent  sac.  With  needles  carefully  sepa- 
rate the  sting  with  the  sac  and  other  accessory  structures. 
Teasing  out  these  structures  can  well  be  accomplished  under 
water,  with  the  aid  of  a  dissecting  microscope  or  binocular.  The 
following  parts  should  be  noted,  drawn  and  labelled: 

a.  The  sting  proper,  consisting  of  two  darts,  ending  in  distinct 
serrations  and  bending  at  the  base  to  either  side  for  muscular 
attachment  and  leverage. 

b.  The  sheath,  partly  enclosing  the  upper  part  of  the  darts, 
and  terminating  in  a  fine  cutting  edge  at  the  distal  edge  of  the 
sting  proper.    It  also  serves  to  direct  the  flow  of  venom  into  the 
wound. 

c.  The  sting  palpi,  situated  on  either  side  of  the  darts. 

d.  The  venom  sac,  emptying  by  means  of  a  broad  neck  into 
the  poison  channel. 

e.  The  poison  gland,  recognizable  as  a  long  coiled  tube  leading 
into  the  anterior  end  of  the  venom  sac. 


EXERCISE  21b 

VENOMOUS  SPIDERS  AND  SCORPIONS 
CLASS  ARACHNIDA,  ORDER  ARANEIDA  AND  ORDER  SCORPIONIDA 

A.  The  most  venomous  of  our  few  dangerous  spiders  is  Lac- 
trodectes  mactans.  With  a  specimen  of  this  spider  before  you, 
note  the  following  characteristics: 

a.  It  is  a  medium-sized  spider. 

b.  The  color  is  brownish  black  to  inky  black. 

c.  Notice  two  brick  red  triangular  spots  on  ventral  side  of 
abdomen. 


PARASITICIDES  37 

d.  Notice  the  comparative  absence  of  hairs  on  the  body  of 
this  species. 

e.  Notice  the  mouthparts.    How  does  the  spider  "bite"? 
Draw  the  specimen. 

B.  Our  commoner  scorpions  are  represented  by  the  three 
genera, — Centrums,  Hadrurus,  and  Uroctonus. 

Examine  a  specimen  for  the  following  characteristics: 

a.  What  is  the  form  of  the  moiUhparts? 

b.  What  is  the  form  and  function  of  the  chelicerce? 

c.  How  many  walking  appendages  has  the  scorpion? 

d.  Examine  the  sting  at  the  tip  of  the  abdominal  appendage. 
Draw  the  specimen. 

C.  Examine  specimens  of  the  whip  scorpion  (Order  Pedipalpi). 


''  //XV2MA/U    < ..'• 

EXERCISE  22 

A^n 

PARASITICIDES 


Poisons  and  repellents.  The  student  should  familiarize  him- 
self with  at  least  a  few  of  the  commoner  materials  used  to  de- 
stroy or  repel  parasites  of  man  and  the  domesticated  animals. 
Samples  of  each  of  the  following  materials  should  be  examined,, 
and  notes  should  be  taken  describing  the  physical  properties, 
such  as  color,  smell,  weight,  whether  liquid  or  solid,  whether 
homogeneous  or  a  mixture,  etc.  Caution!  Do  not  taste  these 
materials;  they  are  Poisons. 

a.  Nicotine  (tobacco  decoction)  is  used  as  a  dip  for  the 
destruction  of  scab  mites  on  sheep  and  also  against  lice  and 
mites  on  other  animals  which  do  not  vomit.  Nicotine  is  a  poison. 
The  proportion  of  tobacco  decoction  used  depends  on  the 
nicotine  content.  "  Black  leaf  40,"  a  commercial  brand,  has  a 
high  nicotine  content.  One  pound  of  a  forty  per  cent  solution  of 
nicotine  to  100  gallons  of  water  (soft  water)  would  make  a  dip 
answering  the  requirements  of  the  U.  S.  Bureau  of  Animal 


38  MEDICAL   ENTOMOLOGY 

Industry  as  used  against  sheep  scab,  but  the  addition  of  sulphur 
(16  pounds  to  the  above  formula)  is  recommended. 
Examine  a  sample  of  tobacco  decoction. 

b.  Lime  and  sulphur  form  the  active  ingredients  for  a  dip 
used  against  scab  mites  of  both  sheep  and  cattle.    When  used 
for  scab  in  sheep  the  following  formula  is  recommended:  24  Ibs.  - 
flowers  of  sulphur,  8  Ibs.  of  unslaked  lime  to  100  gallons  of  soft 
water;  when  used  for  cattle  scab  or  mange,  the  lime  should  be 
increased  to  12  Ibs. 

Examine  a  sample  of  lime  sulphur  solution. 

c.  Cresol  is  a  coal  tar  product  of  high  cresylic  acid  content 
(from  90%  to  98%)  and  is  ordinarily  a  straw-colored  liquid. 
Cresol  is  poisonous,  and  corrosive.     In  order  to  produce  a 
mechanical  mixture  with  water,  cresol  is  carefully  mixed  with  lin- 
seed oil  or  soap,  and  when  prepared  according  to  the  U.  S.  Phar- 
macopeia is  known  as  "  liquor  cresolis  compositus."    As  a  disin- 
fectant, it  is  useful  diluted  with  water  at  from  2  to  4%.    It  is  also 
used  as  an  ingredient  in  sheep  dip.    The  percentage  of  cresol 
used  with  water  depends  on  the  government  rating  of  the  cresol. 

Examine  a  sample  of  cresol,  and  of  liquor  cresolis  compositus. 

d.  Crude  Carbolic  Acid  is  a,  coal  tar  product  with  a  low  phenol 
and  cresylic  acid  content.   It  is  poisonous.    (Pure  carbolic  acid — 
phenol — must  not  be  confused  herewith.)    In  using  carbolic  acid 
as  an  ingredient  for  dips  and  disinfectants,  the  phenol  content 
should  be  known,  since  there  is  considerable  fluctuation  in  the 
amount  of  this  ingredient.    Dilution  with  water  to  2  to  4%  of 
its  phenol  content  is  sufficient  for  disinfection.    For  dipping  the 
same  may  be  said  as  for  cresol. 

Examine  a  sample  of  crude  carbolic  acid,  and  samples  of 
carbolic  acid  crystals,  which  are  pure  phenol. 

e.  Creoline  is  a  coal  tar  product  of  a  low  phenol  content.    It 
is  poisonous.    Creoline  is  much  used  for  dipping  and  disinfection. 
Drop  a  little  in  water  and  notice  the  result.    For  dipping  "pur- 
poses dilute  with  water  to  from  2  to  4%.    It  is  useful  in  destroy- 
ing lice,  and  less  so  for  scab  mites,  on  domesticated  animals. 


PARASITICIDES  39 

For  human  head  lice,  creoline  (2%)  may  be  applied  by  means 
of  a  fine  tooth  comb. 

f.  Kerosene  is  an  extremely  useful  insecticide,  but  must  be 
diluted  to  prevent  injury  to  animals,  and  is  therefore  preferable 
as  a  spray  for  coops  and  stalls  infected  with  mites  or  lice.    Kero- 
sene may  be  used  pure  for  the  latter  purpose,  or  as  an  emulsion 
not  weaker  than  i  to  10.   The  emulsion  is  prepared  by  dissolving 
y£  lb.  of  soap  in  one  gallon  of  hot  water  and  adding  one  gallon 
of  kerosene.    This  forms  a  stock  solution,  and  illustrates  the 
proportion  for  all  practical  purposes. 

Examine  a  sample  of  kerosene  emulsion,  both  in  stock  and 
diluted  one  to  ten. 

g.  Arsenic  may  be  used  as  the  active  ingredient  for  sheep  dips 
and  cattle  dips.    It  is  extremely  poisonous,  and  the  heads  of 
animals  dipped  must  be  kept  out  of  the  solution  and  the  cattle 
prevented  from  licking  themselves  or  each  other.     Persons 
employed  in  dipping  operations  must  proceed  with  caution. 
Dipping  vats  and  stock  solutions  must  be  kept  tightly  closed  to 
prevent  animals  from  drinking  the  poison.    Dripping  animals 
must  not  be  permitted  where  there  is  green  herbage. 

Examine  a  sample  of  arsenic  crystals. 

h.  Pyrethrum  powder,  or  buhac,  is  a  fine  yellow  dust  made 
from  the  flower  of  Chrysanthemum  cinerariafolium.  This 
powder  is  useful  against  lice  and  fleas.  It  is  applied  by  means  of 
an  insufflator  or  duster,  and  must  be  freely  used. 

Examine  a  sample  of  pyrethrum  powder  or  buhac. 

i.  Naphthalene  flakes  are  very  useful  as  a  repellent.  The  flakes 
are  dusted  on  the  animals,  and  brushed  into  the  hair  freely. 
Lice  and  fleas  are  strongly  repelled. 

Examine  a  sample  of  naphthalene  flakes. 

j.  Tobacco  dust  or  snuff,  added  in  equal  parts  or  one  to  three 
of  road  dust  is  extremely  useful  as  a  dust  bath  for  poultry. 
Some  sulphur  may  well  be  added. 

Examine  a  sample  of  tobacco  dust. 

k.  Sulphur  may  be  used  in  cones,  with  wicks,  for  fumigating 


40  MEDICAL   ENTOMOLOGY 

purposes,  or  as  flowers  of  sulphur,  to  be  mixed  with  tobacco 
dust,  as  above,  or  in  the  form  of  an  ointment,  against  scab  and 
mange  mites  on  domesticated  animals,  or  for  human  scabies 
(itch).  An  effective  sulphur  ointment  is  prepared  as  follows: 

Sulphur,  i  oz.,  carbonate  of  potash  y£  oz.  and  lard  4  oz. 

Examine  some  flowers  of  sulphur  and  a  sulphur  cone. 

1.  Formaldehyde  is  a  splendid  disinfectant  and  a  good  stomach 
poison  for  flies,  but  is  useless  as  a  spray  against  insects.  As  a 
fly  poison  formaldehyde  purchased  in  about  38%  to  40%  solu- 
tion must  be  diluted  with  water  to  about  2%  or  even  less,  that 
is,  one  part  to  twenty  or  thirty  parts  of  water.  This  must  be 
made  accessible  to  the  flies  in  shallow  vessels. 

Examine  some  formaldehyde. 

m.  Oil  of  Citronella  is  a  good  repellent  against  mosquitoes, 
black  gnats,  etc.  It  should  be  applied  full  strength  to  the  hands 
and  face. 

Examine  a  sample  of  oil  of  Citronella. 

m.  Larkspur  (Delphinium  staphisagria)  is  useful  in  the  de- 
struction of  both  the  human  head  louse  and  the  crab  louse.  It 
is  ordinarily  used  in  the  form  of  tincture  or  ointment  (Unguen- 
tum  Staphisagria)  10%. 

Examine  a  sample  of  tincture  of  larkspur. 


EXERCISE  23a 

THE  AMCEB.S: 
PHYLUM    PROTOZOA,    CLASS    RHIZOPODA    (SARCODINA),    ORDER 

AMCEB^A 

A.  In  prepared  specimens  on  slide  of  Entamoeba  histolytica, 
the  amoeba  of  Oriental  dysentery,  note  the  following:  (The 
student  is  cautioned  against  confusing  these  with  leucocytes 
and  foreign  matter.) 


THE   TRYPANOSOMES  41 

a.  Outer  clear  portion,  the  ectosarc. 

b.  Inner  granulated  portion,  the  entosarc. 

c.  The  irregular  projections,  the  pseudopodia,  in  which  the 
ectosarc  is  best  seen.    These  are  organs  of  locomotion. 

d.  In  the  entosarc  a  dark  globular  body  is  visible,  the  nucleus. 

e.  Some  specimens  may  show  one  or  more  clear  globular 
bodies  in  the  entosarc,  the  vacuoles. 

Draw  several  specimens. 

B.  Examine  the  slide  for  encysted  amoebae. 


EXERCISE  23b 

THE  TRYPANOSOMES 

PHYLUM  PROTOZOA,  CLASS  FLAGELLATA  (MASTIGOPHORA),  ORDER 
LISSOFLAGELLATA 

A.  In  prepared  samples  of  blood  smears  from  an  animal  af- 
fected with  Nagana,  note  the  presence  of  spindle-shaped  organ- 
isms with  a  whip-like  appendage,  Trypanosoma  brucei,  the  try- 
panosome  of  Nagana. 

a.  A  single  whip-like  appendage,  the  flagellum. 

b.  A  thin  fold  along  the  dorsal  edge,  the  undulating  membrane. 

c.  Near  the  middle  of  the  body  a  dark  object,  the  nucleus. 

d.  Near  the  anterior  end  (the  flagellum  end)  of  the  body,  a 
small  mass  of  chroma  tin,  the  blepharoplast. 

Draw  several  specimens. 

B.  In  a  suitable  blood  smear  from  a  rat,  examine  for  try- 
panosomes,  in  this  case  Trypanosoma  lewisi. 

Compare  A  and  B. 

C.  In  a  blood  smear  taken  from  a  patient  suffering  from  Afri- 
can sleeping  sickness,  first  stage,  examine  for  Trypanosoma  gam- 
biense. 

Compare  this  with  A  and  B. 


42  MEDICAL   ENTOMOLOGY 

D.  Examine  a  specimen  of  Tsetse  fly,  the  carrier  of  A  and  C. 

a.  Examine  the  moulhparts. 

b.  Examine  the  antenna  with  plumose  arista. 

c.  Note  general  form  of  the  fly,  constricted  "  waist." 
Draw  the  specimen  in  outline. 

E.  As  a  matter  of  comparison,  in  a  suitable  preparation  from 
a  fowl  suffering  with  Spirochaetosis,  study  and  draw  the  causa- 
tive organism,  Spirochceta  gallinarum,  and  compare  this  further 
with  Treponema  pallida  of  Syphillis. 


EXERCISE  24 

THE  MALARIA  PARASITES 
PHYLUM  PROTOZOA,  CLASS  SPOROZOA,  ORDER  KffiMOSPORIDIA 

NOTE:  —  It  is  expected  that  the  student  will  read  some  concise 
account  of  the  normal  constituents  of  the  blood  before  proceed- 
ing with  this  exercise,  e.  g.  at  least  the  first  9  pages  of  Chapter  I, 
"  Practical  Study  of  Malaria,"  by  Stephens  and  Christophers. 

A.  Sporozoan  of  quartan  malaria,  Plasmodium  malaria. 

For  this  exercise  use  stained  blood  films  from  malarial  patients. 

Examine  slides  from  cases  of  quartan  infection  (malaria  with 
fever  recurring  every  three  days,  72  hours).  Look  for  pig- 
mented  bodies  inside  of  red  corpuscles.  Determine  the  follow- 
ing stages: 

a.  Small  round  pigmented  body  shortly  after  having  entered 
the  corpuscle. 

b.  Signet  rings,  young  intracorpuscular  parasites. 

c.  The  parasite  nearly  filling  the  corpuscle,  showing  as  a 
deeply  pigmented  body  consisting  of  coarse  granules.    A  num- 
ber of  darker  bodies  may  be  seen  in  the  parasite,  indicating  the 
presence  of  the  micleoli  preparatory  to  sporulation. 

d.  Find  a  corpuscle  showing  the  parasite  in  a  segmented  con- 


THE    MALARIA   PARASITES  43 

dition,  each  spherical  element  provided  with  a  nucleolus  and  the 
eight  or  ten  elements  arranged  so  as  to  give  the  appearance  of  a 
daisy. 

e.  Find  a  corpuscle  that  has  been  broken  down,  thus  liberating 
the  sporulated  parasite. 

Draw  several  stages. 

B.  Sporozoan  of  benign  tertian  malaria,  Plasmodium  vivax. 
Examine  blood  slides  from  cases  of  tertian  infection  (malaria 

with  fever  recurring  every  two  days,  48  hours). 

a.  Note  the  fact  that  the  pigmented  granules  of  this  parasite 
are  considerably  finer  than  in  the  quartan. 

b.  Signet  rings  as  in  A. 

c.  In  the  segmentation  stage  of  this  form  note  the  irregularity 
in  arrangement  of  the  elements  and  their  greater  number. 

Draw  several  stages. 

C.  Sporozoan  of  malignant  tertian  fever,  Plasmodium  pracox. 
In  a  slide  taken  from  an  advanced  case  of  malignant  tertian 

malaria  (aestivo-autumnal  fever)  note  the  presence  of: 

a.  Crescent-shaped   bodies   either   free  or   intracorpuscular 
(usually  only  one  in  a  red  corpuscle).    The  crescent  stage  in  this 
variety  of  parasite  represents  a  condition  just  previous  to  the 
sexual  changes  undergone  in  the  body  of  the  Anopheles  mos- 
quito, or  on  contact  with  the  air  (see  below).    Female  crescents 
have  the  chromatin  massed  centrally  while  the  male  crescents 
have  it  distributed  and  are  hyaline. 

b.  The  parasite  of  malignant  tertian  malaria  (Plasmodium 
pracox)  is  said  to  be  smaller  in  the  mature  form  than  is  the 
benign  tertian  parasite. 

c.  Examine  signet  rings  for  double  nuclei. 
Draw  crescents. 

D.  The  stained  parasites  of  malaria  often  show  ring  forms, 
and  when  stained  with  Romanowsky  stain,  the  red  nucleus  may 
be  between  the  ends  of  the  slender  crescent,  forming  thus  a 
" signet  ring" 

a.  Examine  slides  for  the  "signet  ring"  forms. 


44  MEDICAL   ENTOMOLOGY 

E.  Outside  of  the  corpuscles  in  the  preparations  already  ex- 
amined search  for  flagellated  bodies,  the  microgametes  (sperma- 
tozoans),  or  male  sexual  elements.    These  are  produced  from 
crescent-containing  blood  on  exposure  to  air  for  a  few  minutes. 
(Some  species  do  not  form  crescents  before  flagellation,  e.  g.  the 
benign  tertian  and  the  quartan.) 

F.  In  a  stained  preparation  of  the  salivary  glands  of  a  malaria- 
infested  Anopheles  mosquito  determine  the  presence  of  sporo- 
zotts,  recognizable  as  slender,  slightly  curved  rods. 

G.  In  a  stained  preparation  of  the  midgut  of  a  malaria- 
infested  Anopheles  mosquito,  determine  the  presence  of  sporo- 
blasts,  as  pigmented  bodies  (elongate,  as  sporozoits  when  ad- 
vanced) inside  of  cysts  recognizable  as  wart-like  bodies  external 
to  the  gut. 

H.  As  a  matter  of  comparison  examine  a  blood  smear  of  Texas 
cattle  fever,  and  study  and  draw  the  causative  organism  Babesia 
(Piroplasma)  bigeminum  with  reference  to  form  and  relative 
size.  This  organism  is  carried  by  the  cattle  tick,  Margaropus 
annulatus. 


PART  II 

HELMINTHOLOGY 
INTRODUCTION 

The  object  of  the  following  exercises  is  to  acquaint  the  student 
with  the  commoner  parasitic  worms  infesting  man  and  the  do- 
mesticated animals. 

Formerly  the  term  Vermes  was  used  to  cover  all  groups  of 
worms.  This  group  is  now  divided  into  a  number  of  phyla,  of 
which  the  following  include  parasitic  forms: 

a.  Nemathelminthes.     Commonly   called   thread  worms,   or 
roundworms,  they  are  cylindrical,  non-segmented  animals,  usu- 
ally  more  or  less  tapering  at  both  ends.    The  alimentary 
canal  is  simple  and  well  developed,  except  in  the  Acantho- 
cephala.    The  water-vascular  canals  are  usually  conspicuously 
located  on  both  sides,  longitudinally.    The  sexes  are  separate  and 
development  is  usually  direct,  i.  e.  without  a  necessary  inter- 
mediary host.     Examples  are  the  roundworm  of  the  horse, 
(Ascaris  megalocephala),  and  the  trichina  of  swine,  rats  and  man, 
(Trichinella  spiralis). 

b.  Annelida.    Worms  composed  of  a  series  of  rings,  this  seg- 
mentation often  affecting  the  internal  organs.    The  number  of 
segments  is  usually  large,  a  fact  that  will  differentiate  these 
worms  from  certain  parasitic  insect  larvae,  in  which  the  seg- 
ments are  generally  n  or  12,  never  more  than  19  or  20.    In- 
ternally, of  course,  the  presence  of  a  tracheal  respiratory  system 
will  differentiate  the  latter.    Examples  are  the  common  earth- 
worm (Lumbricus  terrestris)  and  the  medicinal  leech  (Hirudo 
medicinalis).    (The  latter  only  need  be  considered  here.) 

45 


46  HELMINTHOLOGY 

c.  Platyhelminthes.  In  this  group  of  worms  the  body  is  more 
or  less  flattened  dorso-ventrally.  The  digestive  tract  may  be 
entirely  lost,  as  in  the  tapeworms,  or  may  consist  of  a  blind  sac, 
more  or  less  branched,  as  in  the  flukes.  An  anal  aperture  is 
never  present.  The  flat-worms  are  usually  hermaphroditic,  and 
development  in  the  parasitic  species  is  usually  indirect,  i.  e. 
through  an  intermediary  host.  Examples  are  the  pork  tape- 
worm of  man  (Tania  solium)  and  the  liver  fluke  of  sheep  [Fas- 
ciola  (Distoma)  hepatica}. 

To  distinguish  worms  from  insect  larva.  When  insect  larvae 
(parasitic  in  the  body  of  higher  animals)  are  encountered,  there 
may  be  some  difficulty  in  differentiating  them  at  once  from 
worms,  because  of  their  environmental  setting.  Instances  of 
this  are  bots  and  warbles  ((Estridae),  screw  worms  (Chrysomyia 
macellaria)  and  flesh  fly  larvae  (Sarcophagidae)  in  intestinal 
myiasis.  Usually  these  larvae,  are  short  and  plump,  with  well- 
marked  segments,  few  in  number,  usually  n  or  12,  certainly  not 
more  than  20.  Furthermore,  microscopic  examination  will  re- 
veal a  system  of  tubules  in  the  insect,  extending  internally  to 
all  parts  of  the  body,  the  tracheal  breathing  system. 


EXERCISE  25a 

THE  ROUNDWORMS 

PHYLUM  NEMATHELMINTHES,  CLASS  NEMATODA,  FAMILY 
ASCARID^E 

The  roundworm  of  the  horse — Ascaris  megalocephala. 

A.  Characteristics  of  Nematoda.  The  roundworms  or  thread- 
worms may  be  recognized  by  their  cylindrical,  non-segmented 
or  non-jointed  form,  covered  with  a  rather  thick  cuticle,  and 
the  presence  of  a  simple,  well-developed  alimentary  canal;  also 
a  pair  of  lateral  longitudinal  water-vascular  canals,  usually 


THE   ROUND  WORMS  47 

conspicuous.  The  mouth  is  terminal.  The  sexes  are  separate, 
and  the  males  are  generally  shorter  and  more  slender  than  the 
females.  The  development  is  usually  direct  (exceptions)  and 
requires  no  intermediate  host  (exceptions). 

B.  Characteristics  of  Ascaridce.    The  Ascaridae  are  generally 
large-sized  worms  (more  than  2  mm.  in  thickness  at  the  middle 
in  the  typical  Ascarids,  much  less  in  Oxyurids).    The  terminal 
mouth  is  surrounded  by  three  prominent  papillae  or  lips,  one 
situated  dorsally  and  two  ventrally.    The  anus  is  located  ven- 
trally  just  anterior  to  the  termination  of  the  body. 

C.  Examine  specimens  of  Ascaris  megalocephala,  the  round- 
worm  of  the  horse.    This  species  is  chosen  for  use  because  of  its 
convenient  size  and  typical  characteristics. 

a.  Note  sexual  differences  in  size  and  the  presence  of  two 
terminal  spicules  of  equal  length  in  the  male. 

b.  Examine  the  oral  papilla  or  lips,  and  the  ventral  trans- 
verse anal  aperture.    How  can  you  locate  the  dorsal  and  ventral 
sides  of  the  animal? 

c.  Notice  the  two  lateral  longitudinal  water-vascular  canals. 

d.  Measure  the  length  of  several  specimens  in  centimeters. 
Draw  a  specimen  and  label  the  parts. 

e.  Examine  several  posterior  and  median  cross-sections  of  a 
female  Ascaris,  noting  the  presence  of  the  intestine,  and  uterus 
with  ova. 

D.  Examine  other  species  of  Ascaris,  noting  especially  size 
and  color,  viz. : 

a.  Ascaris  lumbricoides  of  man. 

b.  Ascaris  suilla  of  swine. 

c.  Ascaris  vitulorum  of  cattle. 

d.  Ascaris  mystax,  the  mawworm  of  dogs  and  cats. 


\ 


48  HELMINTHOLOGY 

EXERCISE  25b 

OTHER  ASCARIDJS 

A.  Study  mounted  specimens  of  Oxyuris  vermicularis,  the 
pinworm  of  man,  noting, 

a.  The  length  in  millimeters. 

b.  The  form  of  the  body,  tapering  from  the  middle  toward  the 
blunt  anterior  end,  with  thrice  papillated  mouth,  and  terminat- 
ing posteriorly  in  a  fine  pointed  tail. 

c.  What  are  the  sexual  differences? 
Draw  male  and  female  specimens. 

B.  Examine  specimens  of  Oxyuris  curuula  of  the  horse,  and 
the  long-tailed  species  of  the  same  host,  Oxyuris  mastigodes. 

C.  Study   mounted  specimens  of  Heterakis  papillosa,   the 
caecum  worm  of  the  hen. 

a.  Notice  the  three-lobed  lips  or  papilla. 

b.  What  is  the  average  size  and  form  of  this  species? 

c.  Examine   male    specimens,    locating    the    two   posterior 
spiculce. 

Draw  male  and  female  specimens. 


EXERCISE  25c 

THORN-HEADED  WORMS 
PHYLUM  NEMATHELMINTHES,  CLASS  ACANTHOCEPHALA 

The  thorn-headed  worm  of  swine, — Echinorhyncus  gigas. 

A.  Characteristics   of  Acanthocephala.     Ascaris-like   worms, 
with  a  rostrum  covered  with  recurved  hooks;  intestine  absent. 

B.  Echinorhynchus  gigas.    Examine  specimens  of  the  thorn- 
headed  worm  of  the  pig  for  the  following  characters: 


THE   HOOKWORMS  49 

a.  Measure  the  length  of  the  specimens.    How  do  the  sexes 
compare  in  this  respect? 

b.  Examine  the  rostrum  and  note  the  position  of  the  booklets. 

c.  Examine  a  cross-section  of  this  worm. 

d.  How  does  this  worm  procure  its  food? 

Draw  a  specimen  to  show  general  form,  and  make  a  detailed 
drawing  of  the  rostrum,  showing  the  booklets. 

C.  Examine  a  specimen  of  one  of  the  beetles  which  serve  as 
intermediary  host,  e.  g.  Melolontha  vulgaris,  the  European  May 
beetle  or  a  species  of  Lachnosterna.  fe&A 

^'^ 


,         .^ 

EXERCISE  26 

THE  HOOKWORMS 


PHYLUM  NEMATHELMINTHES,   CLASS   NEMATODA,   FAMILY  STRON- 

GYLID.E 

A.  Characteristics  of  Strongylidce.    Nematode  worms  with  six 
circumoral  papillae,  with  or  without  a  buccal  capsule,  in  either 
case  may  have  an  armature  of  teeth  or  hooks.    Females  have 
two  ovaries,  with  genital  pore  usually  posterior,  but  may  be  in 
front  of  middle;  oviparous,  with  direct  development.    Caudal 
bursa  of  males  is  lobed,  each  lobe  with  supporting  rays,  and  two 
spiculae  about  equal  in  length. 

B.  Ankylostoma  duodenale  is  the  European  hookworm  of 
man. 

a.  Measure  length  of  several  specimens,  determining  first  the 
sex. 

b.  Just  inside  the  oral  aperture  notice  the  presence  of  re- 
curved teeth.    How  many  teeth  are  there  in  all  and  what  is  the 
arrangement? 

c.  At  the  base  of  the  buccal  cavity  there  are  also  present 
several  chitinous  processes. 


50  HELMINTHOLOGY 

d.  Notice  the  long  slender  spicules  of  the  males.    Are  they  of 
equal  length  or  not,  and  how  many  are  there? 
Draw  male  and  female  specimens. 

C.  Necator  (Uncinaria)   americana  is  the  American  hook- 
worm of  man. 

a.  How  does  it  compare  with  the  above  species  in  form  and 
size? 

b.  Is  the  buccal  capsule  as  large  as  the  above? 

c.  Compare  the  form  and  arrangement  of  the  teeth  with  the 
above. 

Draw  a  specimen,  showing  only  the  anterior  end  with  buccal 
cavity  and  teeth. 

D.  Strongylus  edentatus  is  the  blood-sucking  strongylid  of 
the  horse.    Examine  specimens  of  this  or  the  related  species, 
Strongylus  (Sclerostoma)  armatus. 

a.  Strongylus  edentatus  is  called  the  "Toothless  Strongylid." 
Are  there  no  teeth  in  the  buccal  cavity? 

b.  Examine  specimens  of  both  males  and  femafes  and  com- 
pare these  with  human  hookworms  as  to  size,  form  and  other 
characters. 

Draw  a  specimen  to  show  general  outline. 


EXERCISE  27 

OTHER  HOOKWORMS 

A.  Monodontus  phlebotomus  is  commonly  called  the  hookworm 
of  cattle,  and  is  the  probable  cause  of  salt  sickness.  Exam- 
ine mounted  specimens  and  make  the  following  determina- 
tions: 

a.  What  Strongylid  characters  do  these  worms  possess? 

b.  Examine  the  large  buccal  capsule,  "provided  at  its  base 
with  a  strong  dorsal  tooth  projecting  into  its  cavity,  and  with 
four  ventral  teeth  or  lancets."    (Ransom.) 


THE   LUNGWORMS  51 

c.  What  is  the  relative  length  of  males  and  females? 
Draw  a  complete  specimen  and  make  a  separate  drawing  of 
one  showing  the  details  of  the  buccal  cavity. 

B.  Examine  a  specimen  of  Monodontus  trigonocephalus,  the 
hookworm  of  sheep.    What  are  the  main  points  of  contrast  with 
the  above? 

C.  Study  mounted  specimens   of   (Esophagostomum  colum- 
bianum,  the  cause  of  nodular  disease  of  the  intestine  of  sheep. 
How  does  this  compare  with  the  bovine-inhabiting  species  as  to 
relative  size  of  buccal  cavity? 

Draw  the  specimen. 

D.  Another  common  Strongylid  parasitic  in  the  intestine 
(fourth  stomach)  of  sheep  is  H&monchus  contortus,  also  a  hook- 
worm, but  possessing  a  narrow  buccal  cavity.     Notice  the 
twisted  condition  of  the  body  in  the  female,  due  to  ovaries 
wound  spirally  around  the  intestine. 

Examine  and  draw  specimens  of  male  and  female. 


EXERCISE  28 

THE  LUNGWORMS 

PHYLUM  NEMATHELMINTHES,  CLASS  NEMATODA,  FAMILY 
STRONGYLID^ 

A.  Dictyocaulus  viviparous  (Strongylus  micrurus)  is  the 
lungworm  of  cattle.  The  worms  inhabit  the  bronchia  and  lungs 
of  young  calves,  especially.  Eggs  are  deposited  in  the  lungs  and 
air  passages  and  are  coughed  out  by  the  host. 

a.  Examine  a  portion  of  the  lung  of  an  infested  calf  in  which 
the  worms  are  present  in  "pockets."  If  available  examine  an 
infested  lung  which  has  been  cut  open.  What  can  you  say  about 
the  distribution  of  the  worms  in  the  lung?  Strongylosis  is  the 
term  applied  to  this  infestation. 


52  HELMINTHOLOGY 

b.  Study  a  mounted  specimen  under  a  low  power.    Note  the 
presence  of  six  circumoral  papilla. 

c.  In  a  stained  female  specimen  note  the  presence  of  two 
ovaries. 

d.  In  a  mounted  male  specimen  notice  the  presence  of  a  pair 
of  caudal  spicules.    Are  the  spicules  of  equal  length?    Examine 
the  caudal  membrane  for  ribs.    How  many  ribs  are  there? 

Draw  both  specimens,  showing  details. 

C.  Examine  a  slide  with  young  and  embryo  Strongylids. 
Draw  an  example  of  Strongylid  larva. 

D.  Study  specimens  of  Strongylus  ovis  pulmonis,  the  lung- 
worm  of  the  sheep.    Describe  the  specimen  and  determine  main 
points  of  difference  as  compared  with  the  above  species. 

E.  Study  specimens  of  Syngamus  trachealis,  the  gapeworm 
of  chicks. 

Draw  a  specimen. 


EXERCISE  29a 

THE  WHIPWORMS 

PHYLUM  NEMATHELMINTHES,  CLASS  NEMATODA,  FAMILY  TRICHO- 
TRACHELLID^ 

A.  Characteristics  of  Trichotrachellidce.  "  Recognizable  by  the 
oesophagus,  which  resembles  a  necklet  of  pearls;  the  anterior 
part  of  the  body  is  usually  of  thread-like  slenderness,  the  pos- 
terior part  of  the  body,  which  contains  the  genitalia,  is  more  or 
less  thickened;  there  may  be  no  spicules  or  only  one.  There  is 
a  single  ovary;  vulva  situated  at  the  border  line  between  the 
anterior  and  posterior  parts  of  the  body."  (Braun.)  In  the 
subfamily  Trichurinae  there  is  a  single  spicule  in  the  male; 
development  is  direct,  without  encysted  larval  stage;  and  eggs 
pass  out  of  the  body  of  the  host  and  do  not  hatch  until  taken 


TRICHINA  53 

into  the  body  again.  In  the  genus  Trichuris,  the  typical  whip- 
worm,  the  anterior  portion  of  the  body  is  of  thread-like  slender- 
ness  and  longer  than  the  posterior  heavy  portion  of  the  body. 

B.  There  are  several  species  of  whipworms  belonging  to  the 
genus  Trichuris,  all  of  which  partake  of  the  characters  above 
mentioned. 

Examine  and  draw  specimens  of  the  following  species. 

a.  Trichuris  (Trichocephalus)  trichuris  is  a  common  whip- 
worm  of  humans.    Note  the  following  characters;  position  of 
mouth,  length  of  thread-like  cesophageal  region  as  compared 
with  the  thick  body;  total  length,  color.    In  a  male  specimen  find 
the  spicules. 

b.  Trichuris  oms  is  a  common  whip  worm  of  sheep,  cattle  and 
goats. 


EXERCISE  29b 

TRICHINA 
PHYLUM  NEMATHELMINTHES,  CLASS  NEMATODA,  FAMILY  TRICHO- 

TRACHELLID.E 

Trichinella  spiralis  is  the  cause  of  trichinosis  of  humans  and 
other  mammals.  The  adult  trichinae  inhabit  the  large  and 
small  intestines  of  several  species  of  mammals,  among  them 
man,  the  domestic  pig  and  the  rat.  The  worms  find  their  way 
into  the  intestine  with  infested  flesh  eaten  by  one  of  the  animals 
mentioned.  In  the  intestine  copulation  takes  place  between 
male  and  female  trichinae;  the  female  gives  birth  to  living  young 
in  great  numbers;  these  are  carried  by  the  lymph  and  blood  to 
many  parts  of  the  body,  finally  finding  lodgment  in  the  muscles, 
where  they  invade  the  connective  tissue  and  even  the  fibres, 
later  becoming  encysted. 

a.  Examine  under  a  compound  microscope  a  prepared  piece 


Ib 


54  HELMINTHOLOGY 

of  diaphragm  of  the  rat  or  pig  infested  with  Trichinella  spiralis. 
Count  the  number  of  cysts  for  a  given  area,  e.  g.  i  sq.  cm. 

b.  Examine  the  specimen  with  the  naked  eye.    Can  you  see 
the  cysts? 

c.  Is  there  any  general  position  that  the  trichina  has  taken 
within  the  cyst? 

d.  Find  trichinae  that  show  advanced  stages  of  calcification. 

e.  Examine  the  adjacent  muscle  fibres  to  determine  effect  on 
the  same. 

Draw  a  characteristic  specimen  of  trichina,  showing  it  in  its 
relation  to  the  muscle. 


EXERCISE  30a 

THE  FILARIJE 

PHYLUM  NEMATHELMINTHES,  CLASS  NEMATODA,  FAMILY 
FILARIIDJ2 

A.  Characteristics  of  Filariida.    "Body  long,  filiform;  mouth 
surrounded  with  papillee,  or  provided  with  two  lips ;  oesophagus 
slender,  without  posterior  bulb.    Males  with  single  spicule  or 
two  unequal  spicules.    Females  with  two  ovaries,  vulva  usually 
in  front  of  middle  of  body.    Usually  oviparous.    Development 
in  many  cases  requires  an  intermediate  host."    (Ransom.)    The 
Filariae  are  extremely  slender  hair-like  worms  inhabiting  the 
blood  and  lymphatic  fluids.    They  range  in  length  from  micro- 
scopic species,  such  as  Microfilaria  bancrofli,  to  the  extremely 
long  guinea  worm,  Filaria  medinensis,  which  probably  averages 
90  cm.  in  length.    (Manson.) 

B.  Microfilaria    bancrofli    (Filaria    nocturna).     Examine   a 
prepared  slide  of  human  blood  taken  from  a  patient  suffering 
from  elephantiasis,  a  disease  caused  by  the  presence  of  filariaa 
in  the  lymphatic  vessels. 


THE   LEECHES  55 

a.  Under  a  moderately  high  power  of  the  microscope,  note 
that  the  filarise  have  an  eel-like  form,  with  the  anterior  portion 
truncated,  while  the  posterior  portion  gradually  tapers  off  to  a 
point. 

b.  Notice  the  clear  sheath  enclosing  the  entire  worm.    The 
mosquito,  Culex  fatigans,  is  the  intermediary  host  for  the 
species. 

Draw  the  specimen. 

C.  Examine  and  draw  filariae  in  a  blood  smear  from  a  ground- 
squirrel. 

D.  Examine  specimens  of  Filaria  ceruina,  a  filarious  worm 
inhabiting  the  peritoneum  of  cattle  and  other  ruminants.    Note 
the  number  of  papilla  around  the  mouth,  the  number  of  spicules 
in  the  male,  and  whether  the  vulva  of  the  female  is  anterior  or 
posterior. 

EXERCISE  30b 

THE  LEECHES 
PHYLUM  ANNELIDA,  CLASS  HIRUDINEA 

A.  Characteristics  of  Annelida  (Annulata).    Worms  belonging 
to  the  Phylum  Annelida  consist  of  a  series  of  rings  or  segments; 
there  are  no  jointed  appendages,  the  alimentary  canal  is  well 
developed. 

B.  Characteristics  of  Hirudinea.    The  leeches  are  character- 
ized by  the  possession  of  a  sucker  at  each  end  of  the  body;  the 
internal  segmentation  and  the  number  of  body  rings  do  not 
correspond. 

C.  With  a  specimen  of  a  leech  before  you,  notice  the  following 
parts: 

a.  The  mouth,  situated  in  the  anterior  sucker. 

b.  The  anus  is  located  dorsal  to  the  posterior  sucker. 

c.  Count  the  number  of  segments  or  annuli. 


56  HELMINTHOLOGY 

d.  Examine  the  buccal  cavity  of  the  specimen  for  jaws.  What  is 
the  arrangement  of  the  jaws?    Some  leeches  do  not  possess  jaws. 

D.  Examine   a   specimen   of   the   medicinal   leech,   Hirudo 
medicinalis. 

a.  Examine  the  jaws  for  teeth. 

b.  What  is  the  color  of  the  specimen,  noting  longitudinal 
striping? 

Draw  the  specimen. 

E.  If  available  examine  and  describe  a  specimen  of  the  horse 
leech,  Hcemopis  sanguisuga. 


EXERCISE  31 

THE  SHEEP  LIVER  FLUKE — DISTOMUM  HEPATICUM 

ORDER  PLATYHELMINTHES,  CLASS  TREMATODA,  ORDER  MALACOCO- 
TYLEA,  FAMILY  FASCIOLID.E 

A.  Characteristics  of  Platyhelminthes.     Body  more  or  less 
flattened  dorso-ventrally;  alimentary  canal,  absent  entirely  in 
the  tapeworms,  consists  of  a  blind  sac  more  or  less  branched. 
No  anus.     Usually  hermaphroditic,  and  development  in  the 
parasitic  species  is  usually  indirect,  i.  e.  through  an  intermediary 
host.    The  phylum  is  divided  into  three  classes:  i,  Turbellaria, 
free  living,  non-parasitic;  2,  Trematoda,  flukes;  and  3,  Cestoda, 
tapeworms. 

B.  Characteristics  of  Trematoda.    Usually  leaf-shaped,  but  in 
a  few  species  conical;  sucking  discs  are  commonly  found  on  the 
anterior  and  posterior  extremities,  and  the  ventral  surface. 
Mouth  is  at  anterior  end,  and  sexual  openings  in  the  ventral 
sucker. 

C.  Characteristics  of  Fasciolida.    One  oral  and  one  ventral 
sucker;  excretory  pore  discharges  at  posterior  border. 

D.  Distomum    (Fasciola)   hepaticum.     This   liver   fluke   in- 


THE  SHEEP  LIVER  FLUKE  57 

habits  the  bile  ducts  of  such  herbivorous  animals  as  sheep, 
goats,  deer  and  cattle.  It  is  a  cosmopolitan  form,  being  found 
in  North  and  South  America,  Europe,  Asia,  Australia  and  Africa. 
In  many  countries  sheep  raising  is  considerably  hampered  by 
liver  rot  caused  by  the  presence  of  these  parasites.  The  species 
undergoes  a  very  characteristic  complex  metamorphosis,  part  of 
which  is  passed  in  the  body  of  a  snail  of  the  genus  Limnaeus, 
and  part  in  the  herbivorous  host. 

Life  history.  The  eggs  are  deposited  by  the  hermaphroditic 
adult  liver  fluke  in  the  bile  ducts  of  the  host,  thence  are  washed 
out  through  these  passages  into  the  intestine  and  pass  out  of  the 
host  with  the  faeces.  If  the  ova  chance  to  reach  water,  the 
ciliated  embryos,  called  miracidia,  emerge.  The  miracidium 
soon  penetrates  the  intermediary  host,  usually  a  small  snail 
(Limnseus)  entering  through  the  pulmonary  passage.  Within 
the  snail  the  miracidium  transforms  into  the  sporocyst,  in  which 
a  number  of  bodies  are  formed,  each  of  which  develops  into  the 
next  stage,  the  redia.  Thus  one  egg  may  give  rise  to  a  number 
of  individuals,  through  this  sporulating  process.  The  redia 
next  develop  into  the  tailed  cercaria,  in  which  condition  the 
intermediary  host  is  abandoned.  The  cercaria  swim  about  in 
the  water,  finally  losing  the  tail,  and  becoming  encysted  on  a 
grass  blade  or  other  plant,  which  is  eaten  by  the  sheep  or  other 
herbivorous  animal,  resulting  in  infestation.  In  some  species 
the  cercaria  bore  into  a  second  intermediary  host,  in  which  they 
become  encysted  and  are  swallowed  by  the  animal  together  with 
this  second  intermediary  host.  Once  within  the  alimentary 
canal  of  the  final  host  the  young  flukes  find  their  way  to  the  bile 
ducts  and  reach  sexual  maturity. 

E.  Structure.  With  several  specimens  of  the  adult  liver  fluke 
before  you,  one  of  which  should  be  stained  and  mounted  in 
balsam,  note  the  following  characteristics: 

a.  Form,  is  leaf-like  and  flattened. 

b.  Suckers,  with  a  hand  lens  note  a  terminal  oral  sucker,  and 
a  -ventral  sucker,  whence  the  name  Distomum. 


58  HELMINTHOLOGY 

c.  Sexual  organs,  just  back  of  the  neck-like  portion,  in  the 
region  of  the  ventral  sucker,  notice  the  coiled  uterus,  yellowish 
in  color,  and  filled  with  eggs.    The  yolk  reservoir  may  be  located 
just  back  of  the  uterus  in  the  median  line,  as  a  dark  colored  more 
or  less  triangular  organ,  two  ducts  leading  to  it  from  the  sides; 
these  ducts  in  turn  lead  off  to  the  finely  branched  yolk  glands, 
seen  as  tiny  dark  spots  on  both  sides  of  the  body.    The  ovary  is 
a  definitely  branched  body  lying  to  one  side  in  front  of  the  yolk 
reservoir.     The  ovary  can  be  easily  distinguished  from  the 
similarly  branched  testes,  which  are  paired,  by  the  fact  that  the 
latter  occupy  the  greater  part  of  the  central  area  of  the  fluke. 
The  ovary  is  usually  darker  and  more  compact.     The  penis 
and  the  genital  pore  are  located  within  the  area  of  the  ventral 
sucker. 

d.  Digestive  system.     This  consists  of  the  mouth,  located 
within  the  oral  sucker,  leading  to  a  prominent  pharynx,  in  turn 
leading  to  the  bifurcated  intestine,  which  lies  along  the  lateral 
margins  of  the  body,  is  much  branched,  and  ends  blindly. 

e.  Excretory  system.    The  excretory  system  may  be  distin- 
guished as  a  median  light  canal  extending  forward  from  the 
posterior  end  of  the  body. 

Draw  the  specimen,  indicating  and  labelling  the  parts  seen. 
F.  Examine  a  portion  of  an  infested  liver,  and  notice  the 
characteristic  lesions  produced  by  the  fluke. 


EXERCISE  32 

OTHER  TREMATODES 

A.  Dicroccdium  (Distomum)  lanceolatum  is  the  lancet  fluke 
of  sheep  and  cattle.    Examine  several  specimens  of  this  species. 

a.  How  does  it  differ  in  size  from  Fasciola  hepatica?      .  b 

b.  Does  the  form  of  the  fluke  justify  the  specific  name? 
Describe  its  form. 


THE  TAPEWORMS  59 

c.  Locate  the  following  parts,  i,  ventral  sucker,  2,  uterus,  3,  in- 
testinal branches,  4,  ovarium. 

Draw  a  specimen,  and  label  all  the  parts  named  in  the  preced- 
ing exercise  that  you  can  find. 

B.  Examine   specimens   of   Fasciola   americana    (Distomum 
magnum)  the  giant  fluke  of  cattle,  infesting  both  the  liver  and 
lungs  of  the  host.    Compare  these  specimens  with  specimens  of 
Distomum  hepaticum,  as  to  size,  shape,  color,  absence  in  this 
species  of  superficial  spines,  etc. 

C.  Paragonimus  westermanni  is  the  lung  fluke  of  man,  occa- 
sionally found  in  other  animals.    This  fluke  is  the  cause  of  a 
Hemoptysis. 

a.  What  is  the  form  and  size  of  this  fluke? 

b.  Locate  i,  the  uterus,  2,  the  ovarium,  3,  two  testes. 
Draw  the  specimen. 

D.  Schisostomum   hcematobium    (this   fluke,    unlike   all   the 
above,  which  are  Distomidae,  belongs  to  the  Family  Schistoso- 
midae)  is  a  Trematode  producing  h&maturia  or  Bilharzia  disease 
of  humans. 

Examine  a  specimen  and  describe  it. 


EXERCISE  33 

THE  TAPEWORMS— A  MORPHOLOGICAL  STUDY 

PHYLUM  PLATYHELMINTHES,   CLASS  CESTODA 

The  following  tapeworm  characters  cannot  well  be  studied 
without  specimens  of  both  the  beef  tapeworm,  T&nia  saginata, 
and  the  fish  tapeworm,  Bothriocephalus  latus,  or  closely  related 
genera,  before  you.  Mounted  and  stained  parts  as  well  as  un- 
mounted specimens  are  needed. 

A.  General. 

a.  Tapeworms  are  more  or  less  ribbon-like  inform. 


60  HELMINTHOLOGY 

b.  The  head,  or  scolex,  is  at  the  tapering  end  of  the  worm,  and 
is  more  or  less  globular. 

c.  Back  of  the  head  are  the  gradually  broadening  segments, 
or  proglottides.    The  oldest  proglottides  are  the  farthest  removed 
from  the  head,  and  these  drop  off  most  readily. 

B.  Under   a   compound    microscope   examine   stained    and 
mounted  specimens  of  heads  and  proglottides  from  T&nia  sagi- 
nata,  the  beef  tapeworm  of  man,  and  Dibothriocephalus  latus, 
the  fish  tapeworm  (closely  related  species  will  serve  just  as  well). 

a.  Head  of  Tcenia  saginata.     Notice  the  four  cup-shaped 
suckers,  and  a  projecting  rostellum,  on  which  there  are  no  hooks. 

b.  Head  of  Bothriocephalus  latus.     Notice  the  presence  of 
two  groove-  or  slit-like  suckers;  the  rostellum  is  absent. 

c.  A  stained  proglottid  (not  too  mature)  of  Tcenia  saginata 
should  show,  i,  the  uterus  as  a  median-branched  tube,  tree-like 
in  form,  which  extends  nearly  the  entire  length  of  the  proglottis, 
2,  the  ovaries,  bilobed,  finely  branched  bodies  situated  in  the 
posterior  end  of  the  proglottis,  uniting  medianally  with,  3,  the 
vitellogene  gland,  situated  along  the  median  posterior  border; 
4,  the  vagina,  a  straight  tube  extending  from  the  median  pos- 
terior field  to  5,  the  genital  pore,  on  the  median  lateral  border; 
6,  the  testes,  consisting  of  a  large  number  of  bodies  distributed 
throughout  the  field  as  fine  dots,  and  joined  by  7,  the  vas  efferent, 
which  again  connects  with  8,  the  vas  deferens,  a  coiled  tube 
paralleling  the  vagina  and  also  connecting  with  the  genital  pore, 
through  9,  the  cirrus  pouch;  10,  the  excretory  system  may  be  seen 
as  two  transparent  collecting  tubes  on  either  lateral  border  (four 
longitudinal  tubes  and  a  transverse  connecting  tube  along  the 
posterior  border). 

C.  Compare  with  the  above  a  stained  proglottid  of  Both- 
riocephalus latus,  the  fish  tapeworm  already  mentioned  in  B,  as 
to  form  and  position  of  the  uterus  and  the  position  of  the  genital 
pore. 

Draw  a  head  and  a  proglottis  of  each  species,  labelling  all  the 
parts  found. 


THE   TAPEWORMS  61 

EXERCISE  34 

THE  TAPEWORMS— A  SYSTEMATIC  STUDY 

PHYLUM  PLATYHELMINTHES,   CLASS   CESTODA 

A.  Characteristics  of  Cestoda.     These  flat-worms  consist  usu- 
ally, in  the  adult  form,  of  a  small  globular  head  or  scolex,  and 
a  chain  of  segments  called  proglottides.    In  the  adult  stage  they 
are  parasitic  in  vertebrate  animals,  having  the  larval  (bladder 
worm)  stage  in  a  secondary  host,  frequently  invertebrate. 

B.  Examine  specimens  of  the  following  species  as  far  as  avail- 
able included  in  the  two  most  important  tapeworm  families. 
The  following  list  is  only  partial,  and  is  meant  to  give  the  student 
merely  a  hint  as  to  classification.    Take  notes  on  the  specimens, 
with  reference  to  characteristics. 

a.  Family    Bothriocephalida.     "Head    provided    with    two 
groove-  or  slit-like  suckers;  rostellum  wanting;  uterus  with 
special  pore;  genital  pores  generally  (possibly  always)  dorsal  or 
ventral."    (Stiles.) 

i.  Genus  Bothriocephalus,  two  elongate  groove-like  suckers 
present;  the  sexual  pore  opens  in  the  mid- ventral  region. 

E.  g.  Bothriocephalus  latus,  the  fish  tapeworm  of  man,  also 
found  in  dogs  and  other  animals  experimentally.  May  reach  a 
length  of  20  to  30  feet,  with  some  4000  proglottides.  The 
middle  proglottides  are  about  three  times  as  broad  as  long.  The 
larva  is  a  plerocercoid  inhabiting  the  muscular  system  of  certain 
fresh  water  fishes. 

b.  Family  Taniida,  "Head  with  four  cup-shaped  suckers; 
rostellum  present  but  not  always  evident;  uterine  pore  wanting; 
genital  pores  generally  marginal;  body  always  segmented." 
(Stiles.) 

i.  Genus  Tania,  scolex  with  a  rostellum  usually  provided 
with  hooks;  mature  proglottides  longer  than  broad;  genital 


62  HELMINTHOLOGY 

pores  projecting  at  the  lateral  borders  and  alternating  irregu- 
larly. 

E.  g.  Tcenia  solium,  the  pork  tapeworm  of  man.  The  ros- 
tellum  is  short  and  is  provided  with  a  double  circle  of  hooks. 
The  average  length  of  the  tapeworm  is  said  to  be  from  8  to  12 
feet,  with  800  to  900  proglottides.  The  mature  proglottides 
measure  from  "  10  to  12  mm.  in  length  by  5  to  6  mm.  in  breadth." 
(Braun.)  The  larva  is  Cysticercus  celMosa,  whose  habitat  is 
the  connective  tissue  of  swine. 

2.  Genus  Dipylidium.     "Rostellum  retractile,  armed  with 
several  transverse  rows  of  alternating  hooks;  hooks  with  small 
roots,  the  base  being  discoidal;  mature  segments  elongate  with 
double  sets  of  genital  organs;  pores  double  and  opposite;  ova 
with  double  transparent  membranes."    (Stiles.) 

E.  g.  Dipylidium  caninum,  tapeworm  of  dogs,  also  found  in 
cats,  and  occasionally  in  man,  measures  from  6  to  12  inches  in 
length.  The  mature  proglottides  are  about  J4  mcn  long  by  y£ 
inch  wide,  and  have  the  form  of  cucumber  seed,  hence  the 
synonym,  Tania  cucumerina.  The  cysticercus  of  this  tape- 
worm is  found  in  the  cat  and  dog  flea,  Ctenocephalis  canis,  and 
the  biting  dog  louse,  Trichodectes  latus. 

3.  Genus  Drepanidot&nia.    "Head  provided  with  a  single  row 
of  uniform  hooks,  few  (8-20)  in  number,  with  dorsal  root  much 
longer  than  ventral  root,  the  latter  always  small;  with  prong 
directed  posteriorly  when  the  rostellum  contracts."    (Stiles.) 

E.  g.  Drepanidotcenia  infundibuliformis  is  a  common  tape- 
worm of  poultry.  This  is  described  as  follows:  "20-130  mm., 
rarely  230  mm.  long.  Head  globular,  rather  depressed;  ros- 
tellum elongate,  cylindrical  or  hemispherical,  swollen  at  sum- 
mit, armed  with  a  single  row  of  16-20  hooks.  .  .  .  Suckers 
rather  small.  Neck  very  short;  anterior  segments  very  short, 
the  following  ones  funnel-shaped,  the  anterior  border  being 
much  narrower  than  the  posterior  border;  posterior  segments 
almost  as  long  as  broad;  genital  pores  irregularly  alternate." 
(Stiles.) 


LARVAL  FORMS  OF  TAPEWORMS  63 

The  cysticercus  of  this  species  is  found  in  the  common  house- 
fly, Musca  domestica. 

Drawings  should  be  made  to  illustrate  the  main  characteristics 
of  the  above  species  of  tapeworms 


EXERCISE  35 

OTHER  TAPEWORMS 

With  the  characters  studied  in  the  preceding  exercises  well  in 
mind  the  student  should  examine  carefully  entire  specimens  in 
formalin  (not  slide  mounts)  of  the  following  species,  taking  notes 
and  making  drawings  such  as  are  necessary  to  indicate  the 
characters  found. 

a.  T&nia  saginata  is  the  beef  tapeworm  (fat  tapeworm)  of 
humans,  the  cysticercus  stage,  Cysticercus  bows,  being  found  in 
cattle. 

b.  Monieza  (Tcenia)  expansa  is  the  broad  tapeworm  of  rumi- 
nants; the  larval  form  is  unknown. 

c.  Tania  coenurus  is  a  tapeworm  inhabiting  the  intestine  of 
the  dog,  wolf  and  coyote.    While  not  dangerous  to  these  hosts 
the  larval  form  is  the  disastrous  gid  parasite  of  sheep. 

d.  Tania  fimbriata  is  the  fringed  liver  tapeworm  of  sheep,  a 
very  injurious  parasite  of  which  the  cysticercus  stage  is  unknown. 

e.  Tania  crassicollis  is  the  thick-necked  tapeworm  of  the  cat. 
The  cysticercus  stage  is  found  in  the  liver  of  small  rodents,  such 
as  rats  and  mice. 


EXERCISE  36a 

LARVAL  FORMS  OF  TAPEWORMS 

Larval    tapeworms    are    known    as    cysticerci    (cysticercus), 
cosnuri  (ccenurus),  or  echinococci  (echinococcus),  depending  on 


64  HELMINTHOLOGY 

the  form  of  development  at  this  stage.  The  cysticercus,  or  blad- 
derworm,  has  a  well-developed  bladder,  in  which  is  found  a  re- 
tracted head  bearing  all  the  characteristics  of  the  adult  tape- 
worm head.  The  ccenurus,  while  inside  of  a  bladder,  like  the 
above,  develops  a  number  of  daughter  cysts,  with  not  more  than 
one  head  in  each,  which  is  capable  of  developing  into  an  adult 
tapeworm  if  ingested  by  a  second  host.  The  echinococcus 
develops  a  number  of  daughter  cysts,  inside  of  which  there*  may 
be  a  number  of  heads.  The  echinococcus  is  ordinarily  much 
more  vesicular  in  form. 

a.  Cysticercus  cellulosa  is  the  larva  of  the  pork  tapeworm  of 
man.     Examine  the  cysticerci  from  the  heart  or  voluntary 
muscles  of  a  pig.    Note  the  size  of  the  object  and  determine  the 
presence  of  a  head. 

b.  Cysticercus  tenuicollis  is  the  diving  bladderworm  of  the  ox, 
and  the  larval  form  of  Tcenia  marginata  of  the  dog.    It  is  one 
of  the  largest  bladderworms,  often  an  inch  and  a  half  or  more  in 
diameter.     The  long,  slender,  invaginated  head  can  be  seen 
through  the  tissue.     Examine  some  bladderworms  from  the 
peritoneum  of  cattle. 

c.  Multiceps  midticeps  (Ccenurus  cerebralis)  is  a  larval  tape- 
worm found  in  the  brain  and  nerve  cord  of  the  sheep,  causing 
the  disease  known  as  gid.    Examine  a  specimen  of  this  ccenurus, 
noting  the  number  of  heads  and  the  characteristics  of  the  same. 

d.  Echinococcus  multilocularis  is  found  in  man,  cattle  and 
swine,  and  is  the  larval  form  of  a  tiny  tapeworm  found  in  dogs. 
The  echinococcus  is  found  primarily  in  the  liver,  but  may  attack 
other  organs.    Here  the  original  cyst  develops  many  daughter 
cysts,  forming  an  alveolar  structure,  often  of  considerable  size. 
Examine  a  section  of  human  liver  affected  with  echinococcus. 

Drawings  of  the  above  types  should  be  made. 


INSECT   LARVAE  65 

EXERCISE  36b 

HELMINTH  OVA 

In  studying  the  characteristics  of  Helminth  eggs  the  following 
from  Manson's  "Tropical  Diseases"  is  suggestive:  "The  points 
to.be  attended  to  in  the  diagnosis  of  ova  are  size,  shape,  color, 
thickness,  roughness,  smoothness  and  markings  on  the  surface  of 
the  shell;  the  presence  or  otherwise  of  yolk  spheres,  of  a  differ- 
entiated embryo,  or  in  the  case  of  the  cestodes,  of  the  three 
pairs  of  embryonic  booklets;  the  existence  of  an  operculum  in 
the  case  of  certain  trematodes  and  of  the  broad  tapeworm 
(Dibothriocephalus).  The  ova  of  the  same  species  of  parasites 
vary  but  slightly,  and  are  in  every  instance  stable  and  definite 
for  correct  diagnosis." 

With  the  above  in  mind,  study,  describe  and  draw  the  following 
species  of  ova: 

a.  Strongylus  ovis  pulmonis,  the  lungworm  of  sheep. 
•   b.  Trichocephalus  trichuris,  the  whipworm  of  man. 

c.  Necator  americanus,  the  American  hookworm  of  man. 

d.  Ascaris  lumbricoides,  the  roundworm  of  man  and  swine. 

e.  Fasciola  hepatica,  the  sheep  liver  fluke. 

f.  Schisostomum    (Bilharzia)    hcematobium,   a    trematode   of 
humans  which  produces  haematuria. 

g.  T&nia  s,olium,  the  pork  tapeworm  of  man. 

I 

EXERCISE  37 

INSECT  LARVE 

This  exercise  is  to  give  the  student  facility  in  distinguishing 
insect  larvae  from  worms,  an  important  matter  when  it  is  neces- 
sary to  trace  modes  of  infection  and  to  administer  remedial 
measures. 


66  HELMINTHOLOGY 

The  following  examples  of  insect  larvae  should  be  studied  care- 
fully, counting  the  number  of  body  segments,  noting  the  presence 
or  absence  of  special  prehensile  booklets,  and  other  external 
characteristics.  Draw  a  specimen  of  each. 

A.  Types  of  insect  larvae. 

a.  Larvae  of  the  horse  botfly,  Gastrophilus  equi;  habitat, 
stomach  of  equine  animals. 

b.  Larva  of  the  ox  warble-fly,  Eypoderma  lineata,  causing 
what  is  commonly  called  "grub  in  the  back"  or  warbles;  habitat, 
the  deeper  layers  of  the  skin  of  bovine  animals. 

c.  Larva  of  the  head  maggot  fly,  (Estrus  oms;  habitat,  nasal 
sinuses  of  sheep  and  deer. 

d.  Larva  of  the  warble-fly  of  rabbits,  Cuterebra  cuniculi; 
habitat,  deeper  layers  of  the  skin  of  rabbits  and  other  rodents, 
commonly  found  in  the  neck. 

e.  Larva  of   the  screw  worm   fly,  Chrysomyia  macellaria; 
which  is  commonly  found  in  wounds  and  open  sores  of  domesti- 
cated animals. 

f.  Larva  of  the  common  blowfly,  Calliphora  wmitoria,  a 
flesh  fly  and  scavenger. 

g.  Larva  of  the  common  housefly,  Musca  domestica. 

B.  Examine  a  dissection  of  a  fly  larva  under  both  low  and 
high  power  objectives,  noting  the  tracheal  system,  an  intricate 
series  of  tubules  ramifying  through  all  parts  of  the  body.    Draw 
several  tracheae. 

C.  Describe  points  of  difference  noted  between  worms  and 
larvae. 

EXERCISE  38 

ANTHELMINTHICS 

While  the  main  object  in  the  present  work  is  to  prevent  infec- 
tion, the  student  should  nevertheless  be  familiar  with  the  com- 
moner agents  used  to  destroy  and  expel  internal  parasitic  worms. 


ANTHELMINTHICS  67 

Owing  to  possible  complications  not  foreseen  by  anyone  but  an 
experienced  physician  or  veterinarian,  the  use  of  anthelminthics 
is  not  recommended  except  under  proper  prescription.  Care 
should  also  be  used  in  handling  such  materials.  A  description 
of  samples  may  be  made,  based  on  whether  the  material  is 
liquid  or  solid,  its  color,  odor  and  other  obvious  characteristics. 

A.  Anthelminthics  for  Humans. 

a.  Pumpkin  or  Melon  seeds  are  useful  when  eaten  fresh  in 
half-ounce  or  ounce  doses,  as  a  preparatory  remedy  to  further 
treatment  for  tapeworms. 

b.  Male  Fern  (Aspidium)  is  used  in  the  oleoresin  form  (Oleo- 
resina  aspidii)  against  tapeworms.    This  is  dangerous  unless 
properly  used. 

c.  Levant  wormseed  (Santonica)  was  formerly  used,  but  has 
been  largely  superseded  by  (d). 

d.  Santonin  (Santoninum)  is  one  of  the  best  remedies  against 
roundworms  (Ascarids). 

e.  Turpentine  is  used  in  diluted  form  as  a  rectal  wash  against 
pinworms  (Oxyuris). 

f.  Thymol  has  been  found  very  useful  in  treating  uncinariasis 
(Necator  americana  and  Ankylostoma  duodenale). 

g.  Pomegranate    (Granatum)    produces   a   volatile   alkaloid, 
Pelletierin,  which  is  useful  for  tapeworm. 

B.  Anthelminthics  for  Domesticated  Animals. 

a.  Areca  nut  (fruit  of  Arecha  catechu)  is  commonly  used  in 
veterinary  medicine  as  an  anthelminthic,  either  alone  or  to- 
gether with  some  other  ingredient,  against  intestinal  worms,  such 
as  roundworms  and  tapeworms. 

b.  Sulphate  of  iron  either  alone  or  together  with  some  other 
ingredient  such  as  arsenious  acid  is  useful  for  roundworms  in 
horses. 

c.  Arsenious  acid  is  used  in  connection  with  sulphate  of  iron 
for  roundworms. 

d.  Oil  of  turpentine,  doses  with  milk  (i  to  16  parts)  dose  2  to 
4  ounces  against  bots  and  other  stomach  worms. 


68  HELMINTHOLOGY 

e.  Common  salt,  powdered  ginger  and  saltpetre  are  used  to- 
gether in  warm  water  against  stomach  worms. 

f.  Tartar  emetic  given  repeatedly  is  a  remedy  recommended  for 
roundworms  in  horses  and  cattle. 

g.  Kamala  is  an  agent  used  in  treating  cattle  for  roundworms 
(Ascarids). 


PART   III 

LIFE-HISTORY   STUDIES   ON  LIVING 
PARASITES 

INTRODUCTION 

The  work  in  the  laboratory  is  made  very  much  more  interest- 
ing and  profitable  if  the  student  has  the  opportunity  of  making 
observations  on  living  animals.  Courses  opening  in  the  first 
semester  come  early  enough  in  the  year  to  make  it  possible  for 
the  student  to  collect  his  own  material  out-of-doors.  For  courses 
beginning  in  the  second  semester  the  instructor  is  cautioned  to 
collect  material  in  the  autumn  and  continue  breeding  through 
the  winter.  This  is  possible  for  at  least  some  of  the  required 
material.  Furthermore,  spring  usually  opens  up  early  enough 
so  that  living  material  can  be  secured  after  the  course  begins, 
and  in  time  to  make  observations  on  the  same.  It  is  advisable 
to  have  either  a  special  breeding  room  or  a  part  of  the  main 
laboratory  set  aside  for  this  purpose. 

By  doing  these  exercises  the  student  secures  a  knowledge  of 
habitat  and  behavior  that  will  be  of  great  assistance  to  him  in 
practical  field  work,  and  the  impressions  thus  secured  will  be 
lasting. 

How  to  Proceed.  The  student  must  secure  his  own  material, 
either  by  securing  the  fully  mature  specimens  (male  and  female) 
and  providing  the  conditions  under  which  eggs  are  deposited,  a 
matter  not  so  easily  accomplished  in  all  cases,  or  by  securing 
the  eggs  in  the  field  under  natural  conditions,  which  plan  is 
recommended.  Breeding  jars  can  easily  be  constructed  of  pint 
fruit  jars  or  smaller  sized  glasses,  covered  over  with  fine-mesh 
bobbinet,  gauze  or  filter  paper. 

69 


yo  LIFE-HISTORY  STUDIES 

Since  this  work  will  go  on  through  the  greater  portion  of  the 
semester  the  student  is  expected  to  collect  his  specimens  early 
in  the  course  and  make  observations  from  time  to  time  to  ascer- 
tain developments.  This  can  be  done  at  the  opening  of  each 
laboratory  period  or  oftener. 

For  notes  the  same  sized  paper  is  to  be  used  as  for  the  exercises 
requiring  drawings.  The  exercise  is  to  be  given  its  regular 
number  and  title.  The  date  of  collection  should  be  indicated, 
together  with  place  and  conditions.  Each  day  observations  are 
made  the  date  should  be  set  down,  together  with  memoranda 
as  to  progress  in  life  history,  continuing  thus  until  the  organism 
has  matured  or  the  term  has  closed.  If  the  specimens  die,  more 
should  be  collected. 

EXERCISE  39 

LIFE  HISTORY  OF  THE  COMMON  HOUSEFLY 

A.  The  student  will  collect  two  or  three  dozen  or  more  of 
housefly  eggs.    These  can  be  collected,  either  from  neighboring 
horse-manure  piles,  or  adult  flies  may  be  captured  and  placed 
in  a  breeding  cage  into  which  is  put  also  a  jar  of  horse-manure. 

B.  Place  the  eggs  into  a  jar  which  is  partly  filled  with  horse- 
manure.    The  jar  should  be  kept  in  a  warm  room.    Cover  the 
jar  with  gauze  or  bobbinet. 

C.  Observe  the  date  on  which  the  larvae  hatch  from  the  eggs. 
You  will  now  have  the  incubation  period. 

D.  Note  the  date  on  which  feeding  ceases  and  full  growth  has 
been  reached.    You  will  now  have  the  period  of  growth. 

E.  After  the  larvae  cease  feeding  they  usually  try  to  leave  the 
manure,  crawling  into  drier  portions  or  nearby  debris  and  pre- 
pare to  pupate.    This  is  called  the  prepupal  period. 

F.  Observe  the  date  of  pupation. 

G.  After  a  given  number  of  days  in  the  pupal  stage  the  fly 
emerges;  it  is  now  an  imago.    If  the  fly  is  to  live  the  student 


LIFE   HISTORY   OF   THE   MOSQUITO  71 

must  provide  a  dish  of  water,  which  may  be  sweetened  with 
sugar. 

H.  Several  days  must  elapse  before  the  fly  is  sexually  mature, 
when  copulation  occurs,  and  the  females  shortly  thereafter  de- 
posit eggs. 

I.  Data  on  the  length  of  life  of  any  animal  is  valuable,  so  that 
the  student  should  endeavor  to  keep  the  flies  alive  as  long  as 
possible,  noting  the  time  of  death. 

J.  Flies  as  carriers  of  bacteria. 

a.  Collect  half  a  dozen  houseflies  out  of  doors,  noting  the 
immediate  environment  and  sex  of  the  individuals.    The  flies 
must  be  collected  in  sterile  vials. 

b.  Prepare  six  sterile  agar  plates. 

c.  Place  the  agar  plates  under  sterile  bell-jars  and  liberate 
one  fly  for  each  plate  and  wait  until  the  flies  have  crawled  about 
on  the  agar. 

d.  Note  the  condition  of  the  agar.    Can  you  see  any  tracks 
that  the  flies  have  made? 

e.  Place  the  agar  plates  in  a  bacteriological  incubator  and 
incubate  for  36  hours. 

f.  What  changes  have  taken  place,  and  what  are  your  con- 
clusions? 

EXERCISE  40 

LIFE  HISTORY  OF  THE  MOSQUITO 

A.  Collect  several  egg  rafts  of  a  common  Culicine  mosquito. 
There  are  usually  pools  of  standing  water,  or  nearby  horse- 
troughs,  on  the  surface  of  which  the  egg  rafts  can  easily  be  seen. 
Count  the  number  of  eggs  in  one  of  the  rafts. 

B.  Place  the  eggs  in  a  pint  fruit  jar,  partly  filled  with  water 
taken  from  the  original  pool. 

C.  Note  the  date  when  the  larvae  (wrigglers)  emerge. 

D.  Change  the  water  in  the  jar  from  time  to  time  by  drawing 


72  LIFE-HISTORY  STUDIES 

out  the  old  water  and  adding  fresh,  using  water  from  the  original 
source  if  possible. 

E.  Observe  the  feeding  and  breathing  habits  of  the  wrigglers. 

F.  Take  several  of  the  wrigglers  from  the  jar  and  place  them 
in  another  jar  of  water.    Then  add  a  few  drops  of  kerosene. 
Note  the  behavior  of  the  insects. 

G.  Observe  the  dates  when  the  wrigglers  cast  their  skins 
(moult). 

H.  After  a  given  number  of  days  the  pupal  (tumbler)  stage  is 
reached.  Observe  breathing  methods. 

I.  If  you  wish  to  save  the  mosquitoes  you  must  now  cover  the 
jars  with  a  screen,  or  preferably  a  glass  funnel,  which  can  be 
plugged  up,  and  permits  one  to  capture  the  mosquitoes  more 
readily. 

J.  Transfer  the  mosquitoes  to  a  breeding  cage  provided  with 
a  dish  of  water.  After  allowing  the  female  mosquitoes  to  have 
a  suck  of  blood,  note  the  date  of  egg  deposition. 


EXERCISE  41 

LIFE  HISTORY  OF  A  FLEA 

, 

A.  Collect  specimens  of  fleas  from  a  dog  and  place  the  fleas  in 
a  glass  vial  covered  with  gauze.    The  females  usually  deposit 
eggs  very  readily. 

B.  After  several  days  the  flea  larvae  will  emerge.     You  must 
now  add  some  moist  sawdust  and  fecal  material  from  rodents, 
or  dry  blood.    The  vials  must  be  kept  in  a  warm  place,  other- 
wise growth  is  exceedingly  slow. 

C.  If  possible  follow  the  growth  of  the  flea  larva  to  the  time 
when  it  spins  a  cocoon  and  pupates. 

D.  Pupae  can  be  kept  under  observation  more  readily.     Note 
the  date  when  the  flea  emerges. 


'TpHE    following    pages    contain    advertisements    of 
books  by  the  same  author  or  on  kindred  subjects 


Malaria,  Cause  and  Control 

BY 

WILLIAM  B.  HERMS,  M.  A. 

Assistant  Professor  of  Applied  Parasitology,  University  of  California;  Officer 

in  Charge  of  Malaria  Investigations  California  .State  Board  of  Health; 

Author  of  "How  to  Control  Mosquitoes  with  Special  Reference  to 

Anopheles,"     "Protecting     California's    Health     Resources 

through  the  Control  of  Disease-Bearing  Insects,"  "The 

Housefly  in  its  Relation  to  Public  Health,"  etc.,  etc. 

Cloth,  Illustrated,  8vo.,  $1.50  net;  postpaid,  $1.63 

The  awakening  of  the  general  public  to  the  necessity  and 
possibility  of  the  control  of  Malaria,  indicated  by  the  incessant 
demand  for  information,  makes  the  publication  of  Professor 
Herms's  concise  treatment  of  the  subject  an  important  and 
timely  event.  The  question  of  Malaria  control  is  deserving  of 
the  most  careful  attention,  particularly  in  these  days  when  so 
much  is  heard  of  the  "  back  to  the  soil "  movement.  For  malaria 
is  notably  a  disease  of  rural  districts.  Those  who  are  familiar 
with  the  situation  know  very  well  that  malaria  is  too  often 
responsible  for  farm  desertion.  Professor  Herms  writes  of  the 
conditions  attending  the  disease  as  he  has  found  and  studied 
them  during  the  past  few  years  himself,  and  the  suggestions  for 
control  which  he  makes  are  such  as  he  applied  with  success. 

The  book  contains  many  illustrations  that  show  in  an  interest- 
ing fashion  the  methods  of  prevention. 

"Nowhere  have  we  found  in  a  single  volume  so  practical  a 
description  of  the  different  phases  of  the  malarian  protozoon, 
the  anatomy  of  the  mosquito  and  the  distinctive  characters  of 
the  different  groups  of  the  mosquito  family." 

— Chicago  Evening  Post. 

"The  author  has  given  us  in  clear  and  simple  language,  many 
helpful  facts."— Boston  Globe. 

"The  book  is  well  illustrated,  the  pictures  of  mosquitoes  and 
of  various  methods  of  combating  the  mosquito  being  particularly 
illuminating." — Philadelphia  North  American. 


THE  MACMILLAN  COMPANY 

Publishers         64-66  Fifth  Avenue         New  York 


Household  Bacteriology 

BY 

ESTELLE  D.  BUCHANAN,  M.S. 
Recently  Assistant  Professor  of  Botany,  Iowa  State  College 

AND 

ROBERT  EARLE  BUCHANAN,  PH.D. 

Professor  of  Bacteriology,  Iowa  State  College,  and 
Bacteriologist  of  the  Iowa  Agricultural  Experiment  Station 

Cloth,  8vo.,  XV+ 536pp.,  index,  $2.25  net 

The  word  Household  is  used  as  an  extension  rather  than  a  limitation  of  the 
title.  In  a  thoroughly  scientific  manner  the  authors  treat  the  subject-matter 
of  general  as  well  as  of  household  bacteriology  and  include,  therefore,  the 
true  bacteria  as  well  as  the  yeasts,  molds  and  protozoa.  The  volume  is, 
therefore,  a  general  textbook  of  micro-biology  in  which  special  attention 
is  given  to  those  problems  which  are  of  particular  interest  to  the  student  of 
household  science.  The  main  divisions  of  the  book  treat  (i)  the  micro- 
organisms themselves,  (2)  fermentations  with  special  reference  to  those 
affecting  foods,  (3)  the  relations  of  bacteria  and  other  micro-organisms  to 
health.  A  fully  illustrated  key  (comprising  37  pages)  to  the  families  and 
genera  of  common  molds,  supplements  the  unusually  extended  discussion 
of  the  morpholo'gy  and  classification  of  yeasts  and  molds,  and  makes  possible 
the  satisfactory  identification  of  all  forms  ordinarily  encountered  by  the 
student.  The  work  embodies  the  results  of  the  most  recent  researches.  The 
book  is  exceptionally  well  written,  the  different  topics  are  treated  con- 
sistently and  with  a  good  sense  of  proportion.  While  concise  in  statement,  it 
is  thorough  in  method  and  scope.  It  is,  therefore,  well  adapted  for  use  as  a 
text  not  only  for  students  of  household  science,  but  also  for  those  to  whom  it  is 
desired  to  present  the  science  of  bacteriology  from  an  economic  and  sanitary 
rather  than  from  a  strictly  medical  point  of  view. 

"The  book  is  a  concisely  written  work  on  microbiology,  a  branch  of 
economic  science  that  the  public  is  beginning  gradually  to  understand,  has 
important  relationship  to  the  total  welfare  and  prosperity  of  the  com- 
munity. .  .  .  The  manual  can  be  recommended  as  a  very  good  elementary 
bacteriology.  It  comprises  about  all  there  is  of  practical  domestic  value." 

— Boston  Advertiser. 


PUBLISHED  BY 

THE  MACMILLAN  COMPANY 

Publishers          64-66  Fifth  Avenue          New  York 


Manual  of  Bacteriology 

BY 
ROBERT  MUIR,   M.A.,   M.D.,   F.R.C.P.,  ED., 

Professor  of  Pathology,  University  of  Glasgow 

AND 

JAMES  RITCHIE,   M.A.,  M.D.,  B.Sc., 

Reader  in  Pathology,  University  of  Oxford 
Nsw  American  Edition  Revised  and  Enlarged  $3.25  net 

"The  American  edition  of  this  well-known  manual  is  perhaps 
one  of  the  best  and  most  comprehensive,  up-to-date  handbooks 
for  the  student  published  in  the  English  language.  The  treat- 
ment of  the  doubtful  questions  is  to  be  commended.  The  in- 
vestigations of  each  observer  and  the  conclusions  are  stated  with 
as  little  bias  as  possible.  ...  An  appendix  furnishes  a  com- 
pact outline  of  the  principal  literature  on  the  different  subjects. 
This  outline  deals  chiefly  with  the  original  works  found  in  the 
foreign  languages." — Medical  Record. 

"Like  Gray's  Anatomy,  Green's  Pathology,  Parkes's  Hygiene, 
and  other  classical  text-books,  this  manual  is  destined  to  remain 
for  years  to  come  the  favorite  of  both  teacher  and  student,  to 
whose  needs  it  is  so  admirably  adapted." 

— Philadelphia  Medical  Journal. 

"A  very  useful  work  for  the  purpose  intended." 

— International  Medical  Magazine. 


PUBLISHED  BY 

THE  MACMILLAN  COMPANY 

Publishers          64-66  Fifth  Avenue  New  York 


Genetics 

An  Introduction  to  the  Study  of  Heredity 

BY 

HERBERT  EUGENE  WALTER 

Assistant  Professor  of  Biology  in  Brown  University 

Illustrated,  12mo.,  $L50  net 

Few  scientific  subjects  are  of  such  interest  and  practical  value 
in  so  many  departments  of  college  work  as  genetics  or  heredity, 
and  in  practically  no  book  previously  published,  has  the  subject 
been  so  treated  as  to  meet  the  requirements  of  the  courses  in  the 
various  departments.  Professor  Walter's  book  is  not  only 
suitable  to  courses  on  heredity,  genetics  or  evolution,  but  also 
to  courses  on  breeding  in  general,  or  on  plant  and  animal  breed- 
ing offered  in  the  colleges  of  agriculture.  It  will  be  found  in- 
valuable as  well,  in  first  courses  on  biology,  or  on  botany  or 
zoology,  offered  in  the  regular  college  curriculum. 

"I  find  that  it  is  a  very  useful  study  for  an  introduction  to  the 
subject.  Professor  Walter  has  certainly  made  one  of  the  clearest 
statements  of  the  matters  involved  that  I  have  seen  and  has 
made  a  book  which  students  will  find  very  useful  because  he 
keeps  everything  in  such  entirely  simple  and  clear  outlines  and 
at  the  same  time  he  has  brought  the  book  up-to-date." 

PROFESSOR  Looms  of  Amherst  College. 

"Within  the  last  generation  the  center  of  biological  interest 
has  gradually  been  swinging  from  the  origin  of  species  to  the 
origin  of  the  individual  and  recent  literature  in  this  field  is 
already  very  large.  This  fact  has  probably  been  one  discourag- 
ing to  non-technical  readers,  who  for  the  most  part  consider 
themselves  too  busily  engaged  to  study  the  subject.  Heredity, 
however,  is  a  matter  which  concerns  everyone,  and  it  is  cause 
for  gratification  that  Herbert  Eugene  Walter  has  summarized 
for  the  uninitiated  some  of  the  more  recent  phases  of  questions 
which  are  at  present  agitating  the  biological  world." 

— San  Francisco  Chronicle. 


PUBLISHED  BY 

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Publishers          64-66  Fifth  Avenue          New  York 


Diseases  of  Economic  Plants 

BY 

F.  L.   STEVENS,  PH.D. 

Professor  of  Botany  and  Vegetable  Pathology  of  the  North  Carolina  College 

of  Agriculture  and  Mechanic  Arts  and  Biologist  of  the 

Agricultural  Experiment  Station 

AND 

].  G.  HALL,  M.A. 

Assistant  in  Vegetable  Pathology  in  the  North  Carolina 
Agricultural  Experiment  Station 

Cloth,  Illustrated,  12mo.,  523pp.,  Price,  $2.00  net;  by  mail,  $2.19 

In  this  volume  only  such  characters  are  used  as  appear  to  the  naked  eye  or 
through  the  aid  of  a  hand  lens,  and  all  technical  discussion  is  avoided  in  so 
far  as  is  possible.  No  consideration  is  given  to  the  causal  organism,  except 
as  it  is  conspicuous  enough  to  be  of  service  in  diagnosis,  or  exhibits  pecul- 
iarities, knowledge  of  which  may  be  of  use  in  prophylaxis. 

While,  in  the  main,  non-parasitic  diseases  are  not  discussed,  a  few  of  the 
most  conspicuous  of  this  class  are  briefly  mentioned,  as  are  also  diseases 
caused  by  the  most  common  parasitic  flowering  plants. 

A  brief  statement  regarding  the  nature  of  bacteria  and  fungi  and  the  most 
fundamental  facts  of  Plant  Physiology  are  given  in  the  appendix.  Nearly 
200  excellent  illustrations  greatly  increase  the  practical  value  of  the  book. 

:    How  to  Recognize  and  Control  Them 

BY 

WALTER  C.  O'KANE 

Entomologist  of  the  New  Hampshire  Experiment  Station,  and 
Professor  of  Economic  Entomology  in  New  Hampshire  College 

Decorated  Cloth,  Over  600  Photographic  Illustrations 

$2.00  net;  postpaid  $2.17 

"This  is,  in  short,  a  book  in  which  others  beside  agriculturists  will  find 
something  of  practical  interest.  The  illustrations  deserve  special  mention. 
They  are  all  originals,  each  subject  being  presented  in  its  natural  size  and 
enlarged  many  times." — New  York  Tribune. 

"After  chapters  devoted  to  the  anatomy  and  physiology  of  insects,  and 
to  the  means  commonly  used  for  protection  of  trees  and  plants,  he  devotes 
the  remainder  to  individual  pests,  giving  descriptions,  and  best  means  for 
extermination.  ...  It  is  most  beautifully  illustrated,  free  from  unnecessary 
technicalities,  and  very  practical." — Chicago  Evening  Post. 

THE  MACMILLAN  COMPANY 

Publishers          64-66  Fifth  Avenue          New  York 


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THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
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